Changing the "My First Badge" awarded on Signup for all users

Visit the Config > Workflow > Rules (SITENAME/admin/config/workflow/rules)

Click the "My First Badge" rule.

Under "Actions," select "Add an item to a list"

On the next page, under "Item to Add" section, in the "eBadge identifier" field, enter the badge ID of the badge you wish to award.  Badge IDs can be found at the "Manage eBadge" page here: SITENAME/staff/ebadges.

Click the "Save" button to save your changes.

Test and confirm that new users are awarded the badge you selected.