Youtube audio post using... iMovie?

I wish to post some audio on YT. I have seen these posted with accompanying illustrative photos for a, for example, 10min recording.
How can I attach a photo or photos to some audio? Using iMovie? I tried doing this but the recording didn't play its duration using the single uploaded photo, but only a few seconds.
Any advice please?

I tried doing this but the recording didn't play its duration

Click to expand...

Select the photo in your iMovie Project, click on the cogwheel and adjust the duration in Clip Adjustments. I think that the max time allowed will be shorter than your music, so do a copy and paste on the photo.

Thanks a lot.