How do I connect Slack usernames to Trello usernames?

[Jesse Chapman]

When I create a board on Slack and assign it to usernames, those usernames are not connecting to anything on the Trello side... it just writes on the board title the user's Slack username, which isn't helpful. 

Ideally, I could say @jessechapman on Slack is @jessechapman345 on Trello or something in a settings and then it would interpret correctly the tags and assign members on the Trello side?

[Theodoro Reato]

Hey Jesse,

You can assign a person to a card through this command:

Add a card
/trello add [teammates] [card name]
Example: /trello add @John @jessica Finish blog post

You can find more information in this article: https://support.atlassian.com/trello/docs/the-trello-app-for-slack/