Press File > Open in the menu.

Navigate to the folder of the game and select the file LF2.EXE

A list of folders will now appear on left, each on those symbolizes different parts of the game.
Press on the + near the folder "Bitmap". 

All the sub-folders in this folder are pictures from the game (opening screens, menus, etc').
To edit a picture, for example the picture BARS (the health bar and the mana bar in the game), do as instructed:
Open the picture, press right click on it and press COPY.

Go to your picture editing program and paste the picture.
Now you can edit the picture as you wish. When you finish, save the picture on the computer and return to ResHacker.
Press Action > Replace Bitmap in the menu.
In the window which will be opened click "Open file with new Bitmap".
Choose your saved picture and press Replace.

For saving the changes press Ctrl + S..
Open the game and see your modification!