Access the group you created.

Select the Group Information icon at the top right corner of your screen.

Select the user you wish to assign as a group admin.

Click on the more icon.

From the drop-down menu, choose Assign as group admin.

Tap the avatar displayed above the screen.

Select the Messages (DM) icon.

Locate and tap the group you created.

Tap the group member icon located at the top right corner.

Choose the desired user to be assigned as a group admin.