Instructions
Press the "Select" button while playing "Mega Man Battle Network 5: Team Colonel" and select "Navi Customizer."
Use your Game Boy's directional pad to select the customizer program you want to compress.
Press the directional pad's right arrow and enter the compression code associated with the selected program by pressing your Game Boy's buttons. You can find a list of compression codes on various websites, such as asia.gamespot.com.