Hi there and welcome
To do this in Gmail, you have to click on the word BCC in the composing email option.
Then on the left in the new window you click on My Contacts and there you choose the Group
Then you can click Select All and then the select button.
It will then add them to the BCC list
If you have any problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.
I can also do these steps for you and show you this directly, and have made a request via Additional Services. This is optional, and if you choose to do this, I can, with your permission, remote into your computer while you watch and do all these steps (and deal with any problems that arise during them) for you. Or if you do not choose to take this service, we can continue here. This is no problem at all. Just let me know please.