How do I add Video Elements into DaVinci?

I’m not sure where to find the answer. I’ve recently become an Envato member. I use DaVinci and have been using the videos from Envato with no problem. I’m now trying to figure out how to add video elements into DaVinci. Do I need to download and remove the Elements from DaVinci every time I finish a project? Are there any videos that can show me how to do this? I appreciate any help anyone can provide.