In simple, modding is a process to improve map's quality and playability by giving suggestions or fixing out potentially unrankable issues. To get a mod, you simply ask a person who can mod, the 'modder' to mod your map.
Modding a map can be done on the "discussion" tab of the map in the browser. Below there are another 5 tabs, but you most likely want to use "General (All difficulties)", "General (Difficulty name here)", and "Timeline".
- General tabs used to mod the map in its entirety, such as metadata, difficulty spread, or general feel of the map.
- Timeline used to mod a specific portion of the map in the chosen difficulty, for example to point out overlapping circles, wrong snap, and such.
To resolve a mod, simply reply your response and click 'Reply and Resolve'. If the mod makes the map feels better to play, it's encouraged to give a like on the post! A mod is not required to be followed in order to make it resolved, though. If you think the modder's suggestion actually makes your map worse, you can reject it by giving a reason why.
You can start finding mappers who will likely mod your map at
Modding Queues, or directly message someone you think can mod your map.
Have fun mapping!