The question you ask is too involved for a proper answer. You may want to go to a car parts store, or book store, and get a repair manual for your car. They cost about $16.00 Or, go to a Public Library.
How do you remove and replace the battery on a 2001 Ford F150?
Replace the Flasher Relay. Located Front seating area, driver side, behind left hand side of instrument panel, on fuse panel.
removetheoldputnewon
How do you remove the inside door panel of a 2001 ford f150.
Pass side firewallbehind kick panel
There are quite a few of light bulbs on the instrument panel. You get to them from the back of the panel. Some instrument panels can be disconnected and pulled forward enough to get to the back, other panels have to be worked on "in place".
Chainsaw
I believe the hazard flasher switch is in the instrument panel by the radio
http://www.svtlightnings.com/svt/how-to/keypad/keypad_install.htm
how to install alternator2001ford f150
How do you replace the tail gate latch on a Ford f150
In the passengers footwell , by the right front kick panel