Your profile — and your post — have that "new Jamf admin" smell, so here we go...
Assuming you got the installer from this page...
First off: don't use the DMG straight off without modifications — that's not how they work in Jamf.
1) Copy the "Cisco Webex Meetings" PKG to the desktop.
2) Upload to Jamf via the cloud panel or Jamf Admin utility.
3) Go to the policy and make sure you've added the package payload with the correct PKG.
4) Scope your policy and save.
5) Run it in self service.
Do you have Jamf Cloud or on-premises, and where is your file distribution server? Are you sure that your managed computers can reach it? Are other policies with software packages working?
You'll also need to check the /Library/Internet Plug-ins folder for any Webex stuff.
Lastly, extensions are a pain in the ass right now in Safari. The WebEx Plugin is not enabled by default; the user must check the box in Safari > Preferences > Extensions after it's installed.
