Prerequisites
Roles required:
Organization Owner/Admin
To assign app to everyone:
The steps vary for the three User Interface versions supported in
Zoho One. Select the UI version you use from the tabs below and proceed
with the steps that follow.
One Experience UI
Sign in to Zoho One , then click Admin Panel icon 
on the top-right corner.Click Portals on the left menu, then click on the Apps tab.
Click the app you want to assign, then click Assign Clients.
Go to the Everyone tab, then click All clients under Rule setting.
Click Assign. Spaces UI
Sign in to Zoho One , then click Directory Settings icon 
on the top-right corner.Click Portals on the left menu, then click on the Apps tab.
Click the app you want to assign, then click Assign Clients.
Go to the Everyone tab, then click All clients under Rule setting.
Click Assign. Unified UI
Sign in to Zoho One , then click Directory in the left menu.
Go to Portals, then click on the Apps tab.
Click the app you want to assign, then click Assign Clients.
Go to the Everyone tab, then click All clients under Rule setting.
Click Assign.