Import image into Media Pool (or use existing image in Media Pool): File > Import > Media....
Drag the image from the Media Pool to the timeline.
Adjust the duration of the still image by dragging its edges in the timeline.
Move the marker to the beginning of the still image clip. And set the position of the image at the beginning of the clip:
Open the "Inspector" panel (if not already open) by clicking on "Inspector" in the upper right corner.
In the "Inspector" panel, under the "Transform" section, adjust the "Position X" and "Position Y" values to move the image to the desired location on the screen.
At the end of the "Position" row, check the diamond box to create a keyframe at the current position.
Move the marker to the end of the still image clip. Adjust the "Position X" and "Position Y" values again to move the image to its final position. A new keyframe will be automatically created.