Hi Femi Famosa,
Thank you for reaching out to us on Microsoft Q&A forum.
Please go to the following link: https://learn.microsoft.com/en-gb/training/modules/model-data-power-bi/3-create-calculated-columns Scroll to the bottom and click the highlighted section.
After that, you can go to the prerequisites and click the highlighted links to download the .pbix file for practice.
If you are still facing any issue, please let us know in the comments. We are glad to help you.
If the information is helpful, please Accept Answer so that it would be helpful to community members.
Thank you.