Start the Fnatic OP, and click on Key Bindings option.
For this example, we have chosen the key 2, so in the upper right corner choose Key 2 instead of FN+2.
Go to Action and click on Default and then choose Open File and under Select File you will be given an option to choose the File and upload it. Once you have done it, choose Save Changes at the right bottom of the page. This way you will be able to bring up the said file with pressing key 2.
If you want to revert it then simply go back to Action, and click Default and then again go to the bottom right to Save Changes.