Since you have not specified the name of the portal you want to update/change your email Id in, I will give you a general idea of how to do it, independent of any portal whatsoever. Let use assume the portal is “ABC PORTAL”
1. Access the ABC Portal
2. Select Control Panel
3. Select Manage Applications
4. Select your organization
5. Select Assign Members in the desired environment
6. Search for the relevant user
7. Deselect the user checkbox
8. Click on Update Assignments
9. Select Users from the left-hand panel of the ABC Portal.
10. Search for the relevant user
11. Select Edit
12. Update the relevant user data fields (e.g. Last name, email address, etc.)
13. Select Save
14. Navigate to the ABC environment (application itself)
15. Go to Administration > Resources, and search for the user
16. Deselect the External Authentication checkbox
17. Click Save and Return, and again access the user profile
18. Edit the relevant fields (e.g. Last Name, email address, etc.)
19. Select External Authentication checkbox and click Save and Return
20. Access the ABC Portal
21. Select Control Panel
22. Select Manage Applications
23. Select your organization
24. Select Assign Members in the desired environment
25. Search for the relevant user
26. Select the user checkbox and click Update Assignments
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath