The TaxAct desktop editions install so that they integrate into the same program file EXE executable). This means that if you have installed multiple federal editions (1040, 1065, 1120, etc.), all editions will run from the same desktop icon or program file.
After installing the federal edition for a return type, to create a new return:
This will create a new return of the selected type (1040, 1065, 1120, etc.) in the program.
To open an existing return for a different form type:
This will open the existing return for the selected form type as long as that product is still installed.