BE Growth tokens (XBE) are Waves assets, create on the Waves Platform.https://wavesplatform.com/. When you download the platform, the user name and password are all you need to buy and sell the BE tokens on the built-in exchange. The platform also has an excellent support function to answer any questions you have: https://support.wavesplatform.com/
If you have troubles please create a support ticket.
Customer support service by UserEcho