get someone to spot you from one side and you keep an eye to make sure front on its straight otherwise you will end up with a crooked hole. You will have to drill out the hole the helicoil tap should say the size of drillbit required. Make sure that when you have tapped the threads for the helicoil that the tap moves easily through the thread. Also put the bolt next to the tap and make sure that the tap goes in about 3-4mm longer than the required length an easy way to do this is mark the thread tap with a pice of electrical tape where you need to stop. When inserting the helicoil with the helicoil insertion thingy (forget the name) and the helicoil has started into the threads use red locktite on the helicoil then proceed to insert it the required depth and then trim the excess.