Go to your minecraft folder, and look in: minecraft > liteconfig > common > heromod for the file named SETTINGS.JSON
you can open that up with something like notepad, word, or notepad++ and see the following entries:
{
"manaRed": 0,
"manaGreen": 0,
"manaBlue": 204,
"manaWidth": 100,
"manaHeight": 20,
"manaOffsetX": 10,
"manaOffsetY": 0,
"partyFrameScale": 0,
"partyFrameAutoScale": true,
"manaBarEnabled": true,
"cdTimerEnabled": true,
"partyFrameEnabled": true
}
with that you can edit the size of the mana bar and it's x and y positions on the screen. The other settings are, if I recall correctly, easily changeable in the in-game menu. Edit the settings to what you want and save it.
But make sure to make a backup of the file first. As I am not very familiar with working with json/java, I am not sure whether they can be saved correctly using a simple text editor or if it requires any sort of special encoding when saved.