All my "users" in one place?

All my "users" in one place?

I signed up today, created 3 users for my business, which are really all me but one is for my vendors, one for orders and one for general support. I want to be able to manage all three from one place and not have to sign in and out bit can't seem to be able to do this. I saw while creating the signature that I was given the option to choose which email to link it to, but again there was only one email. 

Please advise if what I want to do is possible so I don't have to keep signing in and out of three accounts all the time.
Thank you!