Using a .fit file to pace a route on Garmin 840?

Hello, I have a route that I want to try and stay under 4 hrs on. I have done it much faster than that, but thats what I’m hoping is possible with my current fitness.

I have a friends file that I can use as a pacer, but am struggling to figure out how to do that. Leaning towards just taping a piece of paper with the pace at certain landmarks instead of worrying about the Garmin. Any thoughts?

This is on very rough off-road terrain, so I don’t think any sort of virtual pacer would do it.

Garmin virtual partner is what you are looking for.