Select the face of the large rectangular component.
Press CTRL and select the same face on the nearest small component.
In the balloon, click Distance
.
Type a value of 4, and then press Enter.
The result you obtain is not quite what you expect: you do not want the large component to move.
Undo your change.
Create the distance constraint again.
Orient the constraint from the large to the small component by clicking the appropriate option in the balloon.
Arrows indicate the orientation.
Edit the value, entering 4 again.
Notice that the large component remains in the same position.