If you have never contributed to OSM, the process can be pretty easy:
Go walk/hike/bike the trail so you remember what it looks like, perhaps taking notes and recording a GPS trace of it.
Go to openstreetmap.org, make an account, move the map to the area where the trail starts, click "Edit".
If you recorded a trace, drag it into the editor so it can show it as a reference (hopefully it's a GPX, it might be necessary to convert it).
Using the "line" tool, trace the trail, combining the information from the GPS trace, notes and imagery. Make sure to select the finished trace and mark it as a walking/biking/hiking trail. Then click save.
So there is a lot to do, but none of the individual steps are hugely complicated.
If you have never contributed to OSM, the process can be pretty easy:
Go walk/hike/bike the trail so you remember what it looks like, perhaps taking notes and recording a GPS trace of it.
Go to openstreetmap.org, make an account, move the map to the area where the trail starts, click "Edit".
If you recorded a trace, drag it into the editor so it can show it as a reference (hopefully it's a GPX, it might be necessary to convert it).
Using the "line" tool, trace the trail, combining the information from the GPS trace, notes and imagery. Make sure to select the finished trace and mark it as a walking/biking/hiking trail. Then click save.
So there is a lot to do, but none of the individual steps are hugely complicated.