How do i make someone be Co-Owner and UnCo-Owner

[Th0mas_Plays]

I keep forgetting the commands but i wanted my friend to be a co-owner for a while and then unco-own him so pls help me

 

[Ez_Angel]

I keep forgetting the commands but i wanted my friend to be a co-owner for a while and then unco-own him so pls help me

To promote someone on the island use /is promote <player> you can promote that user to co-owner. To remove co-owner do /is demote <user>