@Peace - The following page may help, if their browser is listed here. Otherwise they can search Google for "how to set tbrowser name] homepage" and use the boards URL as the website address they want to use:

https://www.computerhope.com/issues/ch000577.htm

And if anyone on the team is not part of the Miro team where the board resides, you will set the board's sharing setting to Anyone with the link "Can view/comment/edit"​, whichever you need them to be able to do.