Keychain login password

I’m not so well versed with my Mac and now a box has come up asking for my keychain login. I’ve no idea what or where this would be. I’ve followed some instructions using google and it suggests opening up the keychain app in the first instance. Problem is it won’t let me open (I just get the spinning colour wheel).

I cant seem to send emails since this box has appeared either. The whole thing’s gone bonkers. Please help before I chuck it down the garden.