How can I link an appointment to an opportunity?

You can link an appointment to an opportunity within the "Activities Tab".

Link an Appointment to an Opportunity

1. Click on “Activities” to open your activity box.
2. Click and select the particular appointment you want to link (it’s detail window will show-up at the bottom of the activities box).
3. Within the Appointment Tools bar, click on the “Open” button.
4. Click on Browse to search for entity to attach Appointment to.
   
5. Search for the entity in the Look Up dialog and Select.
   
6. Configure other settings for your appointment and click "Save".

Tip: You can link an appointment for a specific opportunity also within that opportunity itself. Open this opportunity (by double-clicking on it) and click the "Activities". Once you create a new appointment for this opportunity, it will be automatically assigned to this it. Since the version 11, it is also possible to link multiple Accounts/Contacts/Leads/Opportunities to the same activity.