I updated my Ubuntu and now i cant download anything with my transimission

I had upgraded my ubuntu software to the newest version and now when i go to download movies, music, or tv shows it wont let me use transmission as a default downloader. Instead when I get to the download box it trys to open the file with VLC video player and when i go to choose another option I cannot find transmission anywhere in the options! even though I have it on my toolbar. I have uninstalled the program and re-installed it and I have searched every application for a way to change the default and I cannot find it anywhere. PLEASE HELP!