How to add a resource pack on minecraft 1.7.4?

Download resource pack (Compatible with 1.7.4)
Open minecraft, goto options -> resource packs. Then click on 'open resource pack folder'
Place downloaded pack in this folder (Should be a zip file)
Restart minecraft, go back into options -> resource packs and click it so it goes under 'Selected resource packs' and it should work.
If not try restart minecraft and it should work.
Hope this helps.