Prerequisites
You must have the Organization Admin role
To approve/reject client sign-up request:
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 Clients tab.
Under the Clients tab, click Sign-up Requests.
Click Approve to allow sign-up or Reject to deny the request. 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 Clients tab.
Under the Clients tab, click Sign-up Requests.
Click Approve to allow sign-up or Reject to deny the request. Unified UI
Sign in to Zoho One, then click Directory in the left menu.
Go to Portals, then click on the Clients tab.
Under the Clients tab, click Sign-up Requests.
Click Approve to allow sign-up or Reject to deny the request.