If you plan to be a team player support, this guide will help you!

Rylai is very fragile, don't try to tank, position yourself properly for fights, lure enemies in since they see you as an easy target.
Be ready to die a lot but it's okay as long as your team wins the teamfight.
Manage wards and vision on the map to help your team. Rylai doesn't rely on items much(1-2 utility items can be plenty for you, you don't right click).
Make sure to stacks camps so your team farms more. This is even easier when your team is not being harassed a lot on lanes or ganked and you can use Q to pull more than 1 camp.

Choose specific items from the guide depending on your game.