If your teacher has invited you to connect on Yousician, you can accept the invite and become their student by following these steps:
1. Open Yousician app and log in with your account details;
2. Open Notifications and accept the new teacher invitation:
Alternatively, you can also accept the invite by going to "Settings" > "Profile" and manage Your Teachers:
If you don't recognise the name of the teacher that has invited you, you can simply tap the "X" button and ignore the invitation. The teacher will not get a notification.