If an owner or admin of another account has added you as their employee, an email will be sent to the address the owner/staff member entered for you. This email will include an invite code.
After you have received an invite code, log into your Jellyfish account
Scroll down in the Menu until you see "My Profile"
On this page, you'll see an "Accept Invite" option. Clicking this will open up a field for you to enter the invite code you received. Once the code is entered, click "Submit".
If your new account is an admin account, you will have access to all sites in the recently added account.
If your new account is a staff member, you will have access to only sites the owner or admin listed.