Go to the Admin Portal, and select Billing & Usage in the left panel. There, select User Management.

Navigate to the user being assigned the access, select the hamburger button against that name, and click on Edit.

In the window that opens, scroll down to the Sales Channel, and click on the field under Select Sales Channel. Check the boxes against the sales channels to which the user is to be granted access.

Under the Select Price Types* and Select Preferred Price Type* headers, the price fields assigned to that sales channel will be auto-filled.

Select Update to save changes.