There are cycling tracks and cycling tracks, some of them belong in OSM, others not.
What belongs in OSM:
- the cyclepaths and lanes on which one bikes
- the signposted cycle routes
What does not belong in OSM:
- you own favorite ride through a national park, following a mix of signposted paths and other roads. This You can upload those to e.g. wikiloc. gpsies, etc.
- Your own preferred streets for cycling (because of low traffic, etc..)
Assuming you want to enter signposted cycle routes, take a look at the [wiki Cycle routes](http://wiki.openstreetmap.org/wiki/Cycle_routes)
You can see the existing cycle routes, e.g. on [the Cycle Map](http://www.openstreetmap.org/#map=15/51.1378/4.3472&layers=C)
Feel free to ask when you get stuck with the documentation on the wiki.