Open the admin left menu and go to Marketing > Integrations (the address is /admin/integrations).

The menu item and the page are only available to users whose role has the Integrations permission (listed under the Business Settings group when you edit a role). Users without it are sent back to the dashboard and, if they try to open a card another way, see the message Invalid Permissions. Some individual buttons have extra requirements: the Connect Stripe button also needs the Stripe Connect permission, and the Plaid Connect account button needs the permission to edit accounting items.