If your existing website was built using Wix, you will only be able to modify the footer.
To access the code, go to the top navigation area and click Code. Then click the button to turn on Developer tools.
This will show an area at the bottom called Site Code. Slide the area up to view the code. You’ll need to copy and past the Accessibility button code into the Site code area using "$w" before the CommonAccess Pro code snippet. See below.
Be sure to Save and Publish.