[Hectic]

What kind of m4?
The battery will either go in the stock (if its a crane stock or full stock) in the handguard (if it doesnt go in the stock)
Or in an external battery box (either a peq type box or a foregrip tyoe box)
If you see the plug for the battery on the outside it goes in a box
If you remove the handguard and see the wire and or if it came with an 8.4 mini bat it gioes in the handguard. If it came with a nunchuck bat and a crane stock it goes in the stock.

Most manuals are generic to their full line of a specific gun (m4 in your case)
Also there is often alot lost in translating from english to ummm chinglish lol.