If you have a regular computer with keyboard and mouse you can use the web application iD - and you will be presented with a satellite photograph of the site which you can trace with your mouse.
You can also use your phone GPS to make a "trace" which is usually a "GPX" format.  These GPX files can be uploaded to OSM, and you can once again trace that to update OSM.
But do take a look at what's currently available, GPX traces still need to be hand processed and perhaps not as good as the already available satellite imagery.