You add users up to your subscription allotment in your Company Settings from the gear icon. If you have no open slots you would have to upgrade. The new users get a time sensitive email to set up their own account to access your company. There is no"exe" even for you as QBO is all online
Thanks for posting to the Community, @cindy47, if you want to add a user, you can go to the Settings icon on the upper right and select Manage Users. This way, you're able to add another user to this page.
There you can assign specific access to a user. Like john-pero said, the users you've added will receive an email invitation to grant access with your QBO account.
If you have reached the limit of adding users, you need to upgrade your plan as to what Fiat Lux - ASIA and john-pero recommended. There you can add additional users.
To get the QuickBooks Online exe file (QBO Desktop App), you can download it through this site by clicking the Download Now button for free: Easier access to QuickBooks Online. Also, if the user has been successfully added, the user can also download this desktop app for free.
You can check the number of users and accounting firms per subscription through these articles: