Hello!
You can insert your own custom text by following the steps below:
1) While you're on the practice screen, click on the "SETTINGS..." button at the upper-right hand corner.
2) Click on the "Provide your own custom text" option under Advanced Mode.
3) Add your own custom text here! Ensure the "Remove punctuation" and "Transform to lowercase" options are left unchecked, as shown in the screenshot.
4) Click on the "DONE" button.
I hope this helps!