To disassemble and replace Hard Drive in laptop asus FX504, you need to unscrew all screws
on the bottom cover of laptop.
Use a plastic tool, to open laptop case.
In description of this video, you can find useful links to various laptop disassembly
tools and parts.
After removing bottom cover, disconnect battery connector
from the motherboard.
Unscrew all screws that hold hard drive
Replace Hard Drive Disk Now you can install a new HDD or SSD drive
Connect the battery connector to the motherboard.
Install bottom case of laptop and screw all screws in the order show on this video guide.