sure i'll help you ^^
now, what you need to do to put your new adoptables in the adoptables category is:
you just have to start a new drawing by clicking in the button that says 'color me in', then, when the oekaki opens, you make whatever you want to make your adoptables banner, or just leave it like you want, and when you finish, you click in the 'save pic' button which is in one of the oekaki boxes. after you click it, it appears a box with 3 options, you click the option 'no, i'll finish it later'.
then, you go to the adoptables board and start a new drawing, when the oekaki loads, you'll see your saved drawings (which you didn't finish) under it. you just have to click your saved drawing, and then save it again, but this time you'll choose the option 'yes, post it now' and after that you'll just have to submit it, and it will appeaar in the adoptables category ^u^
also, to do the new adoptables without changing the banner image, you just have to go to your adotable thread and just click the button 'color me in', just like you do to color these lines

hope you're not confused :p