You can register to Tradeit using your Steam account, here's how:

1. Click 'Log in with Steam' on the top-right corner of the screen

2. Choose the Steam account you wish to use and Click 'Sign In'

3. Enter your Email and your Steam Trade Link and click 'Save'
*If you don't know your Steam Trade Link, you can just click 'Get Link'

4. Once step 3 is done, you will get an Email for verification, just click 'Verify my email address'

That's it. You're good to go!
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