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 this, have a look here.
After the new coach has logged in and registered with the team, he or she can be assigned the role of "Coach". To do this, the current coach must click on the coat of arms symbol to go to the "Team" menu item and select the new coach's profile under Members. In the top right-hand corner of the profile there is the "Edit" icon, which takes you to the new coach's profile details.
Under "Roles & permissions", check the box for the "Coach" role. Once you have ticked the box, save the process. The new trainer now has the correct 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.