1.Refer to https://theshow.com/

2.Find "My Account" on the top right corner.

3.Sign in with your PS/NS/Xbox Account.

4.Click "My Account" on the top right corner.

5.Login your MLB The Show Account(Create an account if your don't have one).

6.Pick the account to continue your progression(choose the account that has game save data)

7.Successfully Linked