A few ways to go about this...

- If you want your new business to use the same name and EIN of your current business you can enable the Online Store for your business and have the Online Store only show the items of the new venture.

-If your new business shares the same EIN (you're running a d.b.a. for example) you can create a new location within your square account. Account and Settings -> Business -> Locations. You can then set up the Online Store for your new location.

-Start a whole new Square account for your new business.

With the last two options, you still control where Square sends the money and you can use the same bank account for that if you want to.