The easiest way to change profiles, is to use the Profile Selector drop down menu in the upper left corner of the program window.
There is a known XOJO issue that can affect a Mac's ability to display a working drop down menu from time to time. A reboot of program or computer usually resolves this.
If you can't use the drop down menu, you can change profiles from within the Profile tab itself.
Double click on the desired profile in the listing, and it will become the active profile.