My first custom ROM flashing related queries

I am using Xperia SP C5303 with stock 4.3 (build 12.1.A.1.207) and CWM installed .
I want to unlock the boot loader via flashtool which I know how to but after that I want to use ArchXperia LP Edition v1.2.4 ROM in my SP.

Guys please tell me after unlocking the BL what should I do?