There are many ways to upload files to Squarespace, but the 2 below ways are common ways that I often use.
A. Use Custom CSS
This way is often used for uploading Custom Font
#1. At Custom CSS, choose Custom Files
#2. Click on the Plus icon (+) to add Images or Fonts
#3. After uploading completely, click on the file, and the file URL will show on the CSS Custom box
B. Upload the file by adding the Link item
This way is used for uploading .css, .js, pdf, image, video,…
#1. In Main Navigation or Not Linked > Click on the Plus icon (+) to add Page
Then you choose Link
#2. Click the URL
And change it to File
#3. Click on this icon to upload the file
#4. After uploading the file, you click CLOSE
#5. To get the link file URL, click on the square icon at the file
Then click COPY the link
