Two different items, so I'm not sure if you're mixing a few terms.
Tags - https://www.wikitree.com/wiki/Help:Tags
- Basically you "tag" something that you want to follow, so that items with that same "tag" appear on your main page "feed" of G2G items or family names that match your tags. The link provides information on how to tag things.
Stickers - I'd say to go to the Help file for stickers, but that can get a little confusing. A sticker is like a project template, in that you put it on a profile that meets the criteria of that project or sticker. For example, if you meet the Notables Project criteria (easiest is if you have a Wikipedia page for that person) then you could put the Notables template or Notables sticker on that profile.
But what I think you might be referring to is neither of these, but possibly "badges"? I'll at least throw that out in case this is what you're asking.
Badges - https://www.wikitree.com/wiki/Help:Badges_and_Points
Badges are awarded for many different reasons. Some by other members who recognize merits of some contribution you've done. Others are awarded by Project Leaders who welcome you into their project effort. If you need more information on Badges than what's in the link, please ask.
