If you want to be easy accessible on Steam, you need to set up a custom URL. This is quite easy and can be done on your profile page here: https://steamcommunity.com/id/me/edit.
After that, use the name you enter for your custom URL as your username. Now people can go straight to your profile and add you as a friend.
In Destiny, players take on the role of a Guardian, defenders of Earth's last safe city, simply called The Last City, as they wield a power called Light to protect the City from different alien races.
The Guardians are tasked with reviving a celestial being called the Traveler, while journeying to different planets to investigate and destroy the alien threats before humanity is completely wiped out.