Make the Hp/Mp bars in some kind of paint program, then import them into the RPG maker pictures.
Now we go to common events, we'll be making two of them.
The first common event turns your character's Hp/Mp into variables. Lets name these variables HP and MP.
The second Common even will tell the game what picture to show, so tell it
IF MP = 1 THEN show picture 01
IF MP = 2 THEN show picture 02
This of course would have to be done with every number, so you would have to make 99 if your character has 99 hp... ._.
That's why, with this method it's best to only do every 10, with bars. So if your char has 99 hp... then they would have 9 bars of HP.
I'm sorry I wasn't very thorough. I have a headache and I fell sick... so I can't really think straight. If you have any questions just ask.