Hi there,
I once had Login Security turned on but disabled it for some reason and now I can't activate it again. I don't seem to know my admin password and don't see any options to reset.
Note: I have a subscription for Hub Protect with Remote Admin. not sure if that complicates things.
If you are not locked out, try to delete the existing login account by clicking the "x", and then create another one with a new password. Please note that local hub login account is not the same as Hubitat Account as used to log into my.hubitat.com.