Hi and welcome!
First off, I don't have either of your pieces of equipment but midi is midi so perhaps I can get you started.
Make sure the cabling's right! Take from the OUT on the M50 to the IN on the Alesis. Make sure both units are cabled to your speakers (obvious I know... but just in case

)
There are two ways to getting them playing together - simplest first:
1. Set the midi channel on the M50 to 1 (there will be a midi tab somewhere in perhaps Global (?) page)
2. Set the midi channel on the Alesis to midi channel 1 in its midi area
3. Again on the Alesis midi or global area, set the clock or metronome (tempo) to EXT
4. Select a good Karma-type rhythm combi and play a chord. The Alesis will play automatically in exact timing with your M50
The other way is to just play the M50 then hit the play button on the Alesis and whenever you hit the button, it will be in sync with the M50:
1. Assuming the M50 midi channel is set to 1, set the Alesis to channel 2 making sure the Alesis clock is set to EXT
2. Play a karma-fied chord - only the M50 will sound
3. At the moment of your choosing, hit the play button at beat 1 of when you want the drums/bass to come in. The Alesis will do its thing in sync with the M50
This should get you started - am not an expert in midi but I do know there's a lot of clever things that can be done, but get the basics right first then move on - I'm sure then others on this forum will help you out.
Hope it helps
