Thanks for the notice. The way to go, and you have already started it, is to propose a merge. That will combine these two profiles. You can see the progress of the merge at the bottom of one of the two profiles, and in your merge feed in the menu.
When both profile managers respond and agree to the merge, the merging is completed. See https://www.wikitree.com/wiki/Help:Merging#Pending_Merges
Probably in this case the other profile manager needs a little bit more time (last activity was in 2019). When the profile manager does not respond in time (about 1 month), the merge becomes public and anyone can complete it.
I would refrain from adding sources to the other profile for now. At the merge step, you have the option to edit the biography. The more duplicate info there is, the more time that takes.