There are a couple of ways;
Click on your own name (above the word ‘Participant’) and select Edit.
Don’t forget to scroll down and click on update.
The other depends on what and how you are viewing the forum. If you see the word ‘MENU’ at the top right, widen the page if possible. Menu will disappear and you will see ‘My Account’ from which you can select ‘Profile’. Then click on ‘Edit Profile’ to change text. You can also select your avatar/thumbnail if you hover over the head figure and click on the little icon that appears top right of the head.
Don’t forget to Save !