Just read the PICBasic manual. within it is a tutorial to get you started blinking an LED. On this forum and also on the MELabs website you will find hundreds of pieces of code... including complete ready-made applications. Take some of those and dissect each instruction. You will find them either in the PICBasic manual, or, in the Datsheet for the relevant PIC.

It's as simple and as complicated as that... we've all had to go through this process sometime, and really there's no short-cut to learning, other than reading, doing, making mistakes and learning from them.