Wikitree IDs, if that is what you are looking for, are in a couple of places when you are on a profile.
- url in your browser has www.wikitree.com/wiki/ <wikitree ID> . To change to a different wikitree ID, if you know it, you just change the ID in the url
- in the yellow / green box 'below' the dates at the top of a profile and 'above' the Biography header. The Wikitree ID is in the 1st green line, under the Profile Manager name