If you still don't have the add ins. Go to the auto desk.com website and search for enablers. Right now I'm going to click on add ins, and for my external tools, I'm going to click the drop down. And I'll go to navisworks 2015. You can save this where you saved your other files. And you can keep the file name architecturally, but before you save it let's look at the settings. Click on navisworks settings, this'll bring up a dialogue. In this dialogue its going to go straight to file readers and to revit.