Place your Play bar (or Scrub bar, or position indicator) in your timeline over the shot you want to filter. Open your title maker and select the background option that displays the shot you want to filter in the title screen.
Select a solid box from the Shapes menu and draw a box covering your entire frame, extending outside the frame on all sides.
In the "Fill" or "Color" box, choose the color you want your filter to be, whether it's black, brown, yellow, orange or some other.Select "Linear gradient" as your fill style. Enter or drag the angle of the gradient to match where you want the graduated filter to be darkest--at the top, the bottom, the left or the right.
Go to the linear-gradient adjustment settings and select the icon/button that represents the "bottom" end of your title box (sometimes this is a slider bar, sometimes it's a box). Make sure it's the same color as the one you've already selected. Then set the opacity or transparency for this end to 0. You should immediately see the color in your solid box fade from opaque to completely transparent across the length of your title box.
Adjust the size and position of the box and the transparency parameters to make the filter look good over your image.
Understand that you'll sometimes want to reduce the size of the box to tighten up the distance between the deepest color and the clear edge. More often, you'll want to stretch the box to up to twice the size of your image to create a far subtler color shift across the frame.
Use the slider on the linear gradient settings to fine-tune how quickly your color fades within the box. Then drag your box, especially if it's significantly larger than the frame, to wherever the color shift works best for your image.
Know that, if you have selected any color other than black, you probably cannot set any of your filter to 100 percent opacity. It will look like a solid color bar or band. Adjust your opacity (transparency) to the darkest you think you can use as a filter and still have it look good.
Save your title and drag the title clip into the timeline onto a video layer over the shot you wish to filter. You may need to render the effect for smooth playback.