Within Teamwork Projects, you can change the email address that you use for your account in your profile settings.
Click your profile icon in the top right corner of the screen, and choose Edit My Details from the dropdown menu:
In the edit details modal, go to the Essentials tab. You will have the option here to change the email address associated with your account. Click Update in the lower right to save your changes.
Note: If you are an administrator or the site owner, you can change the email address of other users. You can do this by going to the People section at the top of the screen, hovering over the appropriate user and clicking the edit pencil to the right.
Another way you can do this is by going to the People section at the top of the screen. Select the relevant user, and choose the Edit User button in the upper right.
For more information, see: Adding extra email addresses