Creating a cymbal swell performed in midi (rather than as a previously recorded audio track), is done in a manner similarly to how a real cymbal swell is actually played: namely, a midi note corresponding to a software instrument patch's cymbal is played rapidly over and over, and the track volume level is increased. For a swell that increases and peaks in volume at the half-way point of note playing, and then decrescendo's back to opening volume, adjust the track volume automation accordingly.
Try the cymbal found at Fsharp in Octave C1, using the Orchestral>Percussion>Orchestral Kit patch. You can first set the track timing to be relatively slow, like 100 BPM, and then strike the cymbal every quarter note; use the metronome when recording to assist with getting an even note strike. Then playback the tempo at 16x speed at which it was recorded to get the rapid cymbal strike roll. Add the volume automation as discussed above to get the volume swell.