recording vocals is no easy task. you are now entering the world of knowledge that surrounds what most experts think of as 'real audio engineering'.
what you want to do with the MPC 5000 is get the highest-cleanest sound possible.
so connect your mic, if its a condenser it will need phantom power which the MPC does not offer.
and then with the meter screen, .. make sure you enable HD audio tracks in "song mode".
choose the track you want to record onto, ... and then enable that track.
now the most important part is adjusting the 'record knob' and making sure the little black switch on the back of the machine is switched from "line in" to "mic in". look on the back and you will find it.
now do a lot of vocal testing at the volume level you expect the lyrics to be in.
go ahead and temporarily turn the "effects send" on the "input" tab off, because unfortunately, none of these effects will be recorded when you record vocals!
so after you turn the vocal effects off or set the send amount to "zero".
then, while you test, you ware trying to make the bar on the meter go as high as possible, yet while "never" clipping. you want to get it as close to clipping as you can get, without actually causing it to clip.
in the end, hopefully, you have a good, strong, clean sounding vocal to work with. for a next step, ... might i suggest some EQ or perhaps a little compression?