Look at the very bottom of your profile, on the left side is a heading PENDING MERGES and beneath it
[initiate a merge]
Hit those words and you will be taken into the program for making a merge. Follow the instructions carefully, especially the proper order of the two profiles.
You will choose which of the two profiles to follow at each point (Birth, Marriage, Death etc.) When you have merged you will be given a chance to edit the result, ironing out any duplicates or errors. If necessary there is a method of going back to the starting position, but that is a terrible waste of your time, so just be careful.
It gets a bit more complicated if you are not a manager or at least on the Trusted List of both profiles.