This video will show you how to synchronize audio samples to the project tempo in FL Studio, and also how to detect the tempo of a sample and match the project tempo.
There are several different techniques available. The technique used depends on the type of sample and what you are trying to acheive. Make sure to watch the entire video to learn all the different techniques.

There are many kinds of audio samples, like one shots, drum loops, instrument loops, vocals etc. They all require a somewhat different approach. This video will cover all the available options like how to cut samples, stretch samples, pitch sample, fit sample to tempo and so on.