IBAN stands for International Bank Account Number. It is a maximum of 34 alphanumeric characters that identifies a specific bank account.
The IBAN and other bank details needed to make a deposit can be found by tapping on "Deposit" in the Portfolio screen, then selecting "Bank Transfer" and the desired fiat currency. Next you'll see see a screen with 2 tabs: "Recommended" (SEPA) and "Global Transfer" (SWIFT).
You can tap on any row of the banking details to copy the information, then all you need to do is paste the details in your banking app. Don't forget to include your reference number for SWIFT transfers!
Under the Recommended tab you'll find the SEPA (or "local") bank details, if available for your location. For these transfers your IBAN is unique and you are the Beneficiary, so there is no unique reference number that needs to be included.