how can i install acer laptops battary?

Answer:

Underneath your laptop here should be a latch over the battery door. If you slide the latch the mobile should "pop" (or you should be able to pull) it out. Then, in recent times insert a new one.
Check your Owner's encyclopaedia or go to Acer's website and look below Support.
There should be a sliding latch that holds the battery contained by place.