In order for Allstar to register your previous matches, you first need to link your Steam account to Allstar, then link your Share Codes
1. If your Steam account is not yet linked, go to your Connected Accounts under your Profile, and link your Steam account
2. If your Steam is already linked, head to the Match History page. From here, you should see a bottom banner that asks you to link your Share Codes. Click on Add Share Codes button!
If you are not seeing thebanner, head to allstar.gg/add-share-codes.
3. After clicking the button, you will be prompted to link a Match Token and Authentication Code. To find these codes, click on the Find My Token & Code button that appears.
After you copy and paste both codes into Allstar, click Finish and head back to Match History to view your matches!