To change your name on guild work:

click your name on the top right of the screen then click on settings


From the settings tab you can edit:
1 - Your display name (how your name appears when you post on guildwork sites)
2 - your email for notifications like someone sending you a request or message (please keep this update to your most recent email)
3 - your signature for guildwork sites
4 - your avatar for posting on the sites
5 - your profile's main image

and remember to save by clicking the save button (6.) on the bottom center of the page