do i have to remove the cap of the reservoir to do this and wheres the bleed nut ???? thanks

Yes as you bleed out air and old brake fluid you need to add more (new fluid) to keep the reservoir topped up.....otherwise more air will enter into the system if the level gets too low.
There is a bleed nipple on the brake caliper of each wheel. An Eezi-bleed kit makes it a much easier one-man job:
Halfords | Gunson Eezibleed (http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_20 4645_langId_-1_categoryId_255216)

Gunson Eezibleed - YouTube