To elaborate on what frozenpeas said, I can't find anything on adding a watermark to video through Premiere except for this method.
1. In Photoshop, create a blank image that is the same size of your video.
2. Paste the logo onto the image and name its layer "logo".
3. Resize and posistion the logo to your taste -- in this case, size it down and move it to the upper corner. Pretend you're watching the video in the image window and adjust the logo to where you'd like it to be. (Keep in mind that your television will most likely crop the edges, so move it in toward the center just a little more)
4. Save as a .PSD file with all the layers included. Don't flatten your image!
5. Import the file into Premiere. Since it is a PSD file, you'll be asked which layer you'd like to import. Select "logo".
6. Create a new video track in the timeline and put the logo in it and stretch it across your entire video.
7. Double-check its transparency setting and render away!
Hope this helps! Tell me if you need anything else! -Trevor