You haven't given us much information about exactly what you want to do. What OS are you using? And do you want to use keyword tags or Places tags that can work with geo-tagging metadata? And what do you mean when you say you want to add tags to your collections? That term can have many meanings. Have you created a collection in other software and want to transfer the tag information to Elements?
Or are you a total novice and are unaware that there is a third program called the Organizer (which comes with both Photoshop and Premiere Elements). The Organizer is where you do all of your tagging.
For now, take a look at this Help article and come back if you have more specific questions.