Check this to remain logged in indefinitely or until you logout, in the current browser. You probably should not check this if you are on a computer that is public or shared with others.
Only you can create your personal MemberHub account. Alliance Careers can create a profile record and send you emails but you need to create an account to confirm your email address and login into the portal.
Use the email address from which you are currently receiving messages from Alliance Careers. You can change email address and add more to your account later.