OK, you have a very good start....let's start with a loop though:
;Initial display of menu
gosub ShowMenu
;Main Loop
repeat
;We will add the stuff to constantly update the display here
until #true=#false ;This will make it loop forever
sub ShowMenu
menu clear
menu Window Title Your Current STATISTICS
menu Window Color YELLOW
menu Font Name Times New Roman
menu Font Size 30
menu Font BGColor LIME
menu Text HPLabel 0 10 HIT POINTS
menu Text CurrentHP 230 10 #HITS
menu Font BGColor BLUE
menu Text MANALabel 0 50 MANA
menu Text CurrentMANA 230 50 #MANA
menu Font BGColor LIME
menu Text STAMLabel8 0 90 STAMINA
menu Text CurrentSTAM 230 90 #STAMINA
menu Show 800 270
return
I also cleaned up your menu a little bit...we could probably clean it up a little further later.
Now, state what how you want the display to update (for example: ANYTIME your HP changes, update the menu). Then state what other actions you want (such as: If HP < 20, make it bright RED!)
Once we know what we WANT to do, then we can work through it step by step and implement it!