Start Source SDK.
When SDK is up click on "Create Mod".
Finish the wizard.
Launch Hammer (must be on your mod)
Make your maps.
Test play it.
How to change the background:
First download VMFedit - Nemesis.thewavelength.net
Then download GCFscape - Slackiller.com
Now, go to your steamapps "c:\steam\steamapps\"
then double click on source materials
Extract every background from the GCF
Extract the background to png
run your map
open console "§"
write "sv_cheat 1" then "noclip"
go to a location you want to take your pic
press "print screen"
exit your map
start normal paint
copy it there
open your copyed background and the background01.png
mark everything on copyed background and copy it to background01.png
press "don't edit size"
crop it to the background01.png size
click on enter
click on the menu tab "effects"
click on blur
blur the pic that you want it
overwrite background01.vmf image with your new one
(Video is coming soon)