1. Perform an internet search for <musictheory.net> (which is totally free)
2. Click on Exercises.
3. Scroll down to Interval Ear Training (and click on it)
4. Click on the "gear" in the top right of the screen.
5. For Intervals, highlight the intervals that you would like to practice (unhighlight the intervals you do not need to practice).
6. For Range, drag the bottom button to the left until it reads C4.
Here is a link to go right there: