Just make sure your TIFF file is RGB and a good resolution. When you import it, it should be much larger than your video so that you can zoom right in.
As a matter of interest, how long are your clips and how long did it take for FCPX to make them into a multicam clip? I have given up on using that function as it takes so long that it’s faster for me to just multi layer.
If you look at the bottom left you will see a little box with lines in it. Open that and go to Video which will show the list of clips in your time line. Select which ever one you want and it will take you to that point in the timeline.