To install a new coach in the team, you need the help of the old coach.
The previous coach must add the new coach to the team, just like any other member. If you don't know how to do that, please look here.
After the new coach has logged in and registered with the team, he/she can be assigned the role of "coach". To do this, the previous coach must go to the menu item "Team" and select the profile of the new coach. In the profile there is an icon "Edit" in the upper right corner, which will take you to the profile details of the new coach.
Under "Roles & Permissions", check the "Coach" role. After you have set the checkmark, save the process. Now the new trainer has the right role.
The previous trainer can also remove the role in the same way. However, this is only possible if another member of the team has the "Coach" role.