Advice on new build, where to start.

Hi,

I ordered myself some parts and they are arriving today.
All parts will be here except the damn power supply.

Now, I will go at my local electronic store and buy a power supply for testing purpose only. I ordered a 750W PSU but i think for testing i will do just fine with 500W and not put it one of the GPU's.

Now, this is my first build so i am clueless as to where to start.

I have seen only one video explaining how to so i tough asking around might be a good idea.

Where do i start ?

How to i proceed ?

Thank you !