First, don’t. It’s a dangerous weapon in untrained hands and it’s likely to be a display model. However, if it’s all you have:
1) If you stab and get stuck, give it a quarter twist while pulling out to release the vacuum.
2) Aim for the neck. It has fewer bones to get your blade caught in.
3) Control distance. The katana is a medium range weapon. It is useless in close quarters.
4) Prepare for breakage. Your katana will break. Don’t be surprised. Wear protection if possible to minimize damage.
Just remember, this weapon is not intended for zombies.