1. Add a subject:
* He attended Yale.
* She attended Yale.
* They attended Yale.
2. Turn it into a question with a subject:
* Did you attend Yale?
* Has he attended Yale?
* Have they attended Yale?
3. Make it a dependent clause:
* The student who attended Yale...
* Anyone who attended Yale...
The best way to fix the fragment depends on the context and what you want to convey.