Hi Natalie..W@H is high risk and a very specialist area of work. Managing workers at height using harness systems could prove very challenging for someone who is perhaps a novice themselves. Training to Unit Standards 23229 & 15757 would be a good start and includes rescue planning etc. Lots of providers Site Safe NZ, VHG, SafetyNAction and others. Training is only the start of the journey to get to competence. Maybe get an appropriately qualified and competent person to conduct a Height Safety Audit for you and go from there. cheers all the best..