Users are able to have a single email address that is associated with multiple organisations within IWTS, however you can only be logged into one at a time.

1 - From your IWTS homescreen click on your organisations name in the left navigation column, then select Settings.

2 - You'll be brought to your account screen where you will see a drop down box with the organisations name you are currently logged in as, select this box to expand it and choose which organisation you wish to switch to. Then select the blue Change Organisation button. You'll now be switched to the chosen organisation.