Remove existing path

This depends which editor you are using:

• iD (standard web editor): select the path and right mouse click on it, bottom option (waste bin) allows you to delete it
• Potlatch 2 (alternative web editor): select the path, either hit the delete key, or choose the waste bin icon on the little toolbox
• Josm: select the path, and hit the delete key. With josm you do have to watch that editor focus is on the map otherwise the delete key will, for instance, delete tags.

Alternatively (and it is more work) you can drag nodes of the existing ways to a better alignment. Only bother with this option if you believe the paths as mapped are merely inaccurate, rather than a misinterpretation of what is actually on the ground.

Editors will complain about you deleting stuff: this is because one of the classic problems we have is people removing stuff which isn't relevant to them because they did not realise that they are editing the common map data