Finish the 1st shoot'em up section then on the screen that follows (The Armoury), move the pointer to the box with the word shield in it (upper left hand corner). Now hold down the '+' key on the numeric keypad and press fire. Allocate all energy to the weapons.
The following keys will now be available during play:
'F6'-----------Replenish life meter
'F1'----Finish shoot'em up sections
'2'-'9'--------------Select weapons
'0'------------------Another weapon
'-'------------------Another weapon
'='------------------Another weapon
'1'-------------Remove extra weapon