A T5018 or T1204 slip is an information only slip provided to a contractor and the CRA. It details the amount you were paid to perform certain services. This is different than T4 employment income (where you’re an employee, instead of a contractor).
Add the relevant section (the Government Service Contract Payments or the Statement of Contract Payments) to your return and transcribe the information from your slip. You’ll then be prompted to select a T2125 slip (or add a new one) to properly report your business income.
You need to report these amounts on a T2125 (Statement of Business or Professional Activities) since they are self-employment income.
If you need help completing the T2125, please refer to this help post.