How to change your nickname per server (PC Tutorial)
Step One: Click the down arrow next to the server name. This brings up the following menu.
Step Two: Click change nickname, this pops up the following screen.Type in your Overgrow username.
Click Save. That's it, you're nickname now matches your OG nickname, this is saved per server, so it won't affect your other discord servers/channels you frequent.
Step One: Click the three dots next to the server name.
Step Two: Click the change nickname option
Step Three: Enter your OG username and click save.
I don't have an android so I can't make a tutorial for that, but it's probably the same idea as IOS.