Drag and Drop Gradients

Have the Gradient window open for the fractal you are working on.
Open a browser window (Ctrl+B)
On the icon bar on the main window use the dropdown to change the file type to 'Gradient Files'. This dropdown is just to the left of the '?' on the row of icons just below the menu.
Navigate to the 'Gradients' folder and open (click-on) an .UGR file.
Now you can drag and drop any gradient from the browser window to your open gradient window.

You may have to resize or move windows around so that you can see both the browser window and the gradient window.