Bass ??? loop ??? problem...

Hello i'm cooking on some nice beats now.
I've got my mpc for a month and since i joined the forum i keep jumping on the ladder of skill.
(here comes the but)

But,
At the moment i'm only F'ing around with the MPC 2500 AD kit. To get more used to the machine.
Because i want to know how to make a proper bassline.
I'm came from the world of trackers ( Impulse Tracker, Fast Tracker, Renoise,FL, Reason).
I've noticed in the AD kit there's a sound that's looped on Pad 1 (TRI).
Wich enables me to use the 16 levels and then play a melody, and the mpc will play the sound as long as i press a pad.
Now i'm trying to do the same with a Bass-sample-loop like this.

1. Open Sample
2. Go to trim
3. Set Start, Loop and End point.

And for as long as i stay in the trim mode, the bass-sound is doing exactly what i want it to do.
4. Extract it as a new sample
5. Put the sample under another pad
6. And hear it's still not looping.

What am i doing wrong.
Can someone tell me?
I would love it if you took me trought from step 1 so i can follow, because sometimes i can't find the functions you guys already can.

Thanks.

Think i didn't read right....

MOdplug tracker is the shit!.LOL..

It may be a dumb question , but it's the dumbest things that often get overlooked.
Is your pad set to "note on" ?

P.S.: i live like 8km from you , first time i see someone living this close to me on the forum