Remove all screws from the bottom case.
Insert a guitar pick or card, pry up and remove the bottom case.
When the bottom case removed, you be able to get access to the battery, hard drive, speaker module, RAM, heat sink and cooling fan.
Here are Dell Inspiron 15 7548’s heat sink and cooling fan module.
My target is replaced the hard drive by a 2.5″ SSD. The new SSD is Samsung 850 EVO 500GB SSD.
Remove the HDD caddy from hard drive.
Install the HDD caddy on the Samsung 850 EVO 500GB SSD.
Install the SSD into the laptop.
Dell Inspiron 15 7548 has two RAM slots.
The RAM is covering by a black tape.
Remove the black tape. Under the black tape, you can access two RAM slots.
This Dell Inspiron 15 7548 features an 4GB PC3L-12800S 1600MHz RAM, so you can add another 4GB RAM.