Go to the gallery, and under the single folder there's like a create new folder button
and
you
CLICK
and name the folder
You can make them into sections of "digital art, traditional..." ORRRR you can make them like "rainbow dash.. fluttershy.. OCs, Derpy"
and to add comments, on the gallery page at the top there is an edit page button (just like your profile
) and you can add stuff
On the fav page and journal page and all the pages there's one