OK , what you do is remove the locknut on the rebound rod , and push the rebound rod up thru the cartridge , it is removed from the inside , you do not touch the screw on the inside you are showing in the pic..... that holds the rebound stack/valving you don't need to mess with it .....
The kit you have will not include the seal you need , you will need to buy it from one of the suspension companies I mentioned , I personally use Race Tech you want seal # FSTC-CS1217 ,12.0x17x3 Blu TC ....the seal is about $10.00 I would recommend replacing both sides since you have everything apart , that is up to you ... ..... So after you get the seal/s , you remove the rod and you will hold the cartridge upside down , you will see a large Allen fitting where the rod went thru .... this is where the seal you need to replace is .... you will need to clamp the cartridge upside down in a vice , either with soft jaws , or a rag wrapped around it to keep from damaging it .....
You will now see 4 small indents in the side about a inch down from the end , these need to be drilled out carefully , using a bit the same size as the hole , be careful as to not drill thru as it will screw up the threads and make removal difficult as well as compromise the cartridge threads when unscrewing , you just need to drill till the bit breaks free (you will feel it bottom out , stop there)
It will look like this , see the holes in the tube ?? , they are peen dents , holding the seal end in place , you need to clear the peen by drilling the tip of the dent out so you can unscrew the assembly ..
You need to use a (will most likely need to buy one) 17mm Allen socket and a half inch breaker bar , or long ratchet along with a torch to heat up the Loctite holding the seal in .... you unscrew the seal (it will be real tight at first) , then remove it (careful it will be hot) then remove the seal , taking note as to the orientation of the seal , put in the new seal , clean off the threads of the nut with Brake Cleaner , and wipe it down and blow it dry with air ..... then use the blue loctite and screw it back on till it is flush
This is the socket , I got mine at Harbor Freight (17mm)
(this pic shows Red Loctite , but I use blue so it can be taken apart another time easier)
Then take the Rebound rod , and cover the threads in Teflon Tape (that white tape you use for plumbing pipe threads and to keep your clutch and brake perch able to move freely on your bars in the event of a crash
Wrap enough of it on the threads and over the tip of the rod that you can rub your finger on the threads and not feel the sharpness of them (the rod threads are extremely sharp and will cut the new seal if you do not wrap them , if you run your finger on them before using the tape you will see what I mean)
Put some fork oil or grease on the threads and tip of the rod , then insert the Rebound rod back into the cartridge carefully , you might need to use a long screwdriver (phillips) or a long punch to push the rod down in so it comes out thru the seal , pull the rod down , reinstall the locknut , then put the cartridge back in the vice right side up and fill the cartridge as you did before and bleed the Rebound rod ..... What I do is fill the cartridge with about 6.4 oz. of fork oil , then bleed the rebound rod by slowly pushing it up into the cartridge , then pulling it back out till it is extended all the way , repeat this using a bit more force each time till you are giving it a strong pull , but still slow so you don't blow all the oil back out when you pull on the rod , as you do it you will get the feel for it , if oil is squirting up out of the tube you are pulling too hard and too fast , then use your flashlight to look down in the cartridge and look for bubbles , if you see ANY then keep bleeding , you want to pull fast enough and with enough force to open the valving to allow the oil to bypass , this is how it is bled is to get the oil from underneath , back into the main chamber , then pour some oil on the O-Rings of the Fork Cap Assembly , then slowly insert the Fork Cap Assembly into the cartridge rocking it side to side as you go , it will take some force , but it will go down to the threads , then use the fork cap wrench and push down while tightening , it should begin to thread in , snug it down by hand with the wrench , you do not need to torque it , and then push in on the rod and you should have pressure and the rod should be extended fully and when you push it in it should return to full extension , if it does not , then you need to pull out the Fork Cap Assembly again and rebleed the rod until all the fine bubbles are completely gone , and you should be good