What preparation do I need to do before I use anti-foul on my small yacht?

My husband has just brought a small 23ft yacht and it needs to have a revamp inside and out,the boat has been out of the water for just over a year and the survey said it was in very good condition, the hull needs to have "anti-foul" put on before it goes back into the water, (it is GRP construction). What is the best way to do this and what preparation do we need to do?