Dell Inspiron 15 (N5040, Mid 2011) - Manual (Page 14)

14 Battery
Replacing the Battery
1 Follow the instructions in "Before You Begin" on page 9.
2 Slide the battery into the battery bay until it clicks into place.
3 Slide the battery lock latch to the lock position.
1 battery release latch 2 battery
3 battery lock latch
1
2
3