I am assuming you are asking this question because your refund went down. If you are filing your taxes, you will need to include ALL your income, in the proper tax year, regardless of the effect it has on your return. This is especially true this year with the passage of the Protecting Americans against Tax Hikes Act or PATH ACT. If your return has Earned Income Tax Credit (EIC) or the Additional Child Tax Credit and you leave off income, then it will cause your refund to be held up for further review. In addition, if he IRS believes income was purposely left off, especially to help with EIC calculations, you could end up being barred from using the EIC for several years.
However, if you are just looking to remove the W-2 to check out certain things then you can click on the Federal Income link, and then follow the screens. you should see your W-2 entries and can edit or remove any erroneous entries.