Follow these links for guides on how to find your username for the different types of social media available on 1social.
Instagram
Youtube
Facebook
Google+
Pinterest
Snapchat
Flickr
Messenger
Medium
Reddit
Linkedin
Steam
Twitch
Paypal

The following are pretty straight forward:
twitter

The following are developer related, I assumed that you know how to find your username:
Hackernews
Github
Keybase
Devpost
Dev.to
Angel

The following do not support any link sharing, instead a username is shown:
Discord (no link)
Origin (no link)