I want to put the RF module in my enclosure? What do I need to be careful of?

If the case is plastic, putting the antenna inside is fine. However, it is important to keep the antenna as fully extended as possible with the tip furthest away from any ground conductors eg. shield case, PCB, antenna radials. The electric field/potential is concentrated at the tip and any metal nearby will nullify any radiation.
If the case is metal, antenna cannot be placed inside and will need to be mounted on the casing itself. Most 1/4 lambda antenna connections use a thread/nut at the base for mounting so the metal this antenna is mounted to will become the ground plane for the RF radiation.