Moving BNB as BEP2 from binance.us to Binance Chain Extension Wallet

First, if you haven't done so already, install Binance Chain Extension Wallet and create an account. Once you are logged in to the wallet, and click Receive, as shown in this screenshot:

Next, click "copy" button next to your address, as shown in this screenshot:

Next, head over to BNB withdrawal page on binance.us and paste the address you copied from Binance Chain Extension Wallet into "Recipients BNB Address"

Leave Memo field empty, enter the amount of BNB you would like to withdraw and click "Submit". After that, Binance will send you an email to verify your withdrawal. Check your email and click the confirmation link. Once the withdrawal is confirmed, you will see the BNB in your Binance Extension Wallet. The withdrawal may take from 5 seconds to a couple of minutes depending on how busy the network is.