The way to add a grant opportunity to multiple Projects is by duplicating that opportunity.
1. You can create a duplicate record of any grant by opening the grant page in your tracker, go to the bottom right More Options --> Duplicate
2. On the next screen, you will be asked to which Instrumentl Project you'd like to save it, there you can select the Project you'd like to add this grant to and add any information you'd like to save, such as Amount Requesting, Submission Goal, and any Notes.
3. Hit the "Save" button at the bottom of the screen.