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.
Overwatch puts players into two teams of six, with each player selecting one of several pre-defined hero characters with unique movement, attributes, and abilities; these heroes are divided into four classes: Offense, Defense, Tank and Support. Players on a team work together to secure and defend control points on a map and/or escort a payload across the map in a limited amount of time. Players gain cosmetic rewards that do not affect gameplay, such as character skins and victory poses, as they continue to play in matches. The game was launched with casual play, while Blizzard added competitive ranked play about a month after launch. Additionally, Blizzard has developed and added new characters, maps, and game modes post-release, while stating that all Overwatch updates will remain free, with the only additional cost to players being microtransactions to earn additional cosmetic rewards.