Ford 1998 Windstar Owner's Manual page 181

Seating and Safety Restraints
Insert either the left or right safety belt tongue into the
5.
single opening of the crotch safety belt buckle as shown in
Figure 4. (It does not matter which tongue is inserted first.)
Then insert the other tongue. The color green must appear in
the indicator window on each tongue when buckled.
Figure 4: Fastening the crotch safety belt buckle
181