How can I make title screens in either Illustrator or Photoshop and import them into Premiere Pro?

I'm having trouble finding the identical aspect ratio to import either an Illustrator or Photoshop title screen into Premiere Pro. There are so many ratios to choose from with Premiere Pro that I've about lost my mind. I was able to import Photoshop title screens into iMovie with no problem. I'll be importing the finished video into my YouTube channel. I want it to be widescreen but have no clue which ratio to use. Thanks for any help you can provide.