FYI: I ALSO POST STEFAN+KATHERINE.
Hi! To make photosets, you need to pick your first pic/gif and then you click on + add another photo (just below browse, on the right) and you can add as many as you want. And everytime you pick another one, tumblr offers a bunch of different template/layout at the top and you just click on the one you want. I hope that was clear, I’m really bad at explaining things. :)