I looked up this thread and noticed that the images are broken and I'm guessing it's also outdated
https://www.lfs.net/forum/thread/11182-How-to-use-a-skin-in-LFS-%5Band-upload-to-LFSW%5D

Quote :

If you are a demo racer, you cannot upload skins by default. Only licensed racers get free skin slots. You can however purchase additional skin slots (see the LFS World skins window), so that demo racers can upload skins as well.

Where do I buy these slots when I can't even find where to do it?

It looks like you do it from the skin upload page - https://www.lfs.net/account/skins/upload

I just have the option to add credit, but if you already have some then maybe the option to buy slots is there ?

I have £1 in account and on https://www.lfs.net/account/skins/upload there is blue button "Add 50 extra slots"
So I guess that is how it works, add credits and then click that..
S3 seems to have added some slots too.

Quote from Bean0 :

It looks like you do it from the skin upload page - https://www.lfs.net/account/skins/upload

I just have the option to add credit, but if you already have some then maybe the option to buy slots is there ?

Yeah apparently there it is. Thank you so much for the help.