When in doubt as to exactly what you want to do with the fabric....then do NOTHING! Don't cut it. It may need to sit on the shelf awhile awaiting for that perfect project it was bought for.
If you're wanting to use it for borders then wait until the entire rest of the top is completed. You will then block if needed, iron and starch your top. Then after measuring determine what you need for your borders. Then check and measure twice more. Then cut them. If necessary ask someone to check your measuring before cutting.
Audition the fabric against the top and get opinions.
Check out several tutorials here, google search and You Tube videos about borders.
Good luck with your quilt. Please keep us updated as you progress through your project and share pictures if possible.
Pam M