1. Login to your Expression Engine Control Panel
2. Click the Admin tab
3. Click 'Members and Groups'
4. Click 'View Members'
5. Select the username whose password needs reset
6. Click the + icon next to 'Personal Settings'
7. Click 'Username and Password'
8. Fill in 'New Password' and 'New Password Confirm'
*When you are a 'Super Admin' user, you do not need to fill in the 'Your Existing Password' field, despite the message saying you must.
9. Click Update