if you are using a BBQ lighter that has the button and the two wires comeing out of the back then you need to put to opposing bolts or screws and attach one wire to one and another to the other . then it is up to you on how you light it. I have a friend who had a plug with a long (5ish ft) wire so he would just hold it in his hand while some one else held the gun. PS. If the igniter doesnt have two wire then there should be a common ground and another connection.
It's not a good idea to use the ignitor in the hole leading to the combustion chamber. BBQ ignitors were never made to take that kind of stress. That is why I recommend using a sparkplug, and then simply securing the ignitor to the side of the gun. For this, use either tape, glue or a custom bracket. The spark plug will generally stay in the hole if you drilled properly, but you can certainly add a nut to the other side to be safe.