There are a few different ways how you can top up myTU account.
You can add your credit or debit card information - just like a simple payment, you will be able to add a selected sum whenever it is necessary.
The minimal limit for a single top up is 5 EUR. The maximum limit is 1000 EUR. There is a monthly limit of 2000 EUR.
You can make a SEPA transfer to your myTU account. To see your International Bank Account Number, go to the Settings page and press "Accounts".
You can send a request to your fellow myTU users by using the option in "Add Money". The transactions should be reflected in your balance immediately.