How do intermolecular forces affect vapor pressure?

through aiding or impeding molecules' haphazard motion.

A gas's vapor pressure is the force it applies to its liquid or solid state; the greater the vapor pressure, the greater the probability that the liquid or solid's molecules will overcome atmospheric pressure, become liberated, and transform into gas.

The intermolecular forces are one of the many factors that affect the "breaking loose" phenomenon. The stronger these forces are, the more tightly packed molecules are, and the more difficult it is for them to break loose.

That should have addressed your query.

Sources & Additional Reading: Intermolecular Forces and Vapor Pressure

Intermolecular forces affect vapor pressure by influencing the ease with which molecules can escape from the liquid phase into the vapor phase. Stronger intermolecular forces result in lower vapor pressure because more energy is required to overcome these forces and escape into the vapor phase. Conversely, weaker intermolecular forces lead to higher vapor pressure as molecules can more easily break away from the liquid phase.