Open the Products tab from your Dashboard.

Then, select the Product you would like to customize.

Click Customize.

There, hover over the image and click Customize to enter the Theme Editor.

Open the dropdown menu at the bottom of the sidebar and select Post.

In the sidebar, select Post Sidebar or Action Buttons depending on your Product Theme.

Then, click Downloads.

There, enter your desired title in the Downloads field.

Then, click Save: