How to use filters for images

I am a beginner I want to resize images to cover the video frame completely but when I select filter there is no + button to see the drop down menu

Not sure I understand. There is no drop-down menu for filters, they are shown as a ‘list’. Just select from the list.
+ means to add a new filter to the clip.

To resize an image to fill the frame, select the image on the timeline then use the Crop filter and then drag the sliders to adjust the zoom and position how you like

Thanks for your previous reply
I sorted out the filters box but now when I try to resize and reposition the image to fill the screen it seems to cover only half maybe the settings I have altered in error
Please advise

Screenshot? I’m not sure what you mean

The main window above the timeline

Still not sure what you mean by only covering half. You need to adjust the sliders for Top/Bottom/Left/Right.