I recently released my first drum sample library, and several people who are new to sampling and MIDI have inquired about how they could go about using them.
These samples are 24 bit stereo WAV files. Most DAW applications record in WAV or AIF, and they all can read both formats. WAV and AIF are raw, uncompressed audio formats. This means that there's no loss in audio quality, as opposed to MP3, which sacrifices audio resolution in favor of smaller file sizes.
1. Drop the files directly onto the grid
The simplest way to use samples is to simply drop the sounds directly into audio tracks. Create a track for each drum and place the samples where you want them within the measure. This doesn't require using MIDI or software instruments. You can treat the sounds just like you would any audio in your song project.
There's no disadvantage to this approach, although it can be a bit slow.
2. Use a drum machine instrument/plugin
If you use MIDI and some kind of software instrument, you can perform the drums with a keyboard or other MIDI controller.
A drum machine plugin has a container for each drum sound, and often some kind of step sequencer interface for creating beats. One big advantage to this approach is you only need one MIDI track for an entire drum kit. Each "note" that you play on the keyboard or MIDI controller triggers an individual drum sound.
3. Use a sampler instrument/plugin
This approach is like a hybrid of numbers 1 & 2. A sampler plugin is what you use anytime you play an artificial piano or organ sound in your DAW. Every time you press a key, you're playing back a pre-recorded WAV file of a sound via the sampler instrument.
If you instantiate a MIDI track and sampler instrument for each drum sound you want to use, then load a drum sample into each sampler, you can easily perform or draw the MIDI for each drum track. If you want to get fancy, you can use "multisample" configuration wherein you use one track and assign a different sample to each note. That way you could control the entire drum kit with one MIDI track, similar to #2.
4. Use a drum replacer plugin
Nowadays, many records feature acoustic drum performances enhanced or replaced with drum samples. A plugin like Drumagog is inserted on, for instance, a pre-recorded snare drum track. Looking ahead, the plugin detects the transient for each snare hit and alongside it (or instead of it), plays the drum sample. The timing and dynamics of the original performance are preserved, but the sound is replaced.
Hopefully, this post gives you the info you need to get started. Good luck!