Transform text link to button

Site URL: https://www.pa-agency.com/job-senior-pmo

Hi,

I need visitors to upload a file to my form - and for this I had to use a Dropbox-link.
This - however - should be transformed into a button but the steps I followed to do this don't work and the text remains plain text/link.

Can someone help me? 

The text/link is the UPLOAD CV part on the bottom-right of both these pages:

https://www.pa-agency.com/job-senior-pmo

https://www.pa-agency.com/job-open-application

THANKS!

Add to Design > Custom CSS

a.upload {
    border: 2px solid black;
    border-top-left-radius: 10px;
    border-bottom-right-radius: 10px;
    padding: 20px;
}