Hi Mychelle, 

Welcome to the Box Community, I'm happy to help!

If you do not want to grant a user access to an entire folder, and only to a specific file, you can actually do this following the steps below.

With simplified sharing, it takes just moments to invite people to collaborate even on just a specific file:

 To invite someone to collaborate in a file or folder:

1. Open the Share window. To do this, in your Box files view, hover over the row of the file or folder you wish to share.
2. On the right, click Share.
   
   
3. The Share window opens.
   
   
4. In the Share window, under Invite People, click Add names or email addresses.
5. Type a collaborator's name or email address.
   • As you type, Box anticipates your intended recipient and lists corresponding email addresses.  You can select the recipient you want, or continue typing the full email address.
   • When typing full email addresses, separate recipients by a horizontal space.
6. Click the Invite as drop-down menu. Box displays a list of roles.
7. Click the role you wish to assign to the collaborator.
8. (Optional) In the Message field, type a message of up to 750 characters for the collaborator.
9. Click Send.

For more details, please take a look at this article: https://support.box.com/hc/en-us/articles/360043696854-Inviting-Collaborators 

Hope that helps! Thanks for reaching out and let us know how else we can help.

All the Best,