Hire a pro. This is not something you want to mess with, in my opinion, particularly with a pendant light that is not firmly affixed to the ceiling.
You can buy a canopy kit that has a hasp or mounting bracket that will secure the hook of the canopy and the chain of the fixture to a junction box. The wire from the lamp will have one wire smooth and one with ribs running the length of the wire. The ribbed wire connects to the white ( neutral) wire and the smooth side wire connects to the " hot " wire which is generally black. Secure the connection with wire nuts and be sure to connect the bare copper wire ( ground )the mounting bracket. Make sure to turn off the power at the circuit breaker