You can link a task to an opportunity within the "Activities".
Link a Task to an Opportunity
- Click on “Activities” to open your activity box.
- Click and select the particular task you want to link (it’s detail window will show-up at the bottom of the activities box)
- Within the Task Tools bar, click on the “Open” button.
- Click on Browse to select entity.
- Select entity in the Look Up dialog.
- Configure other settings for your task and click “Save”.
Tip: You can link a task 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 task for this opportunity, it will be automatically assigned to it.