Hi and welcome. The usual advice is to test immediately before eating and two hours subsequently. That shows you how your body dealt with whatever carbs were consumed. Carbs when digested turn to glucose. Everyone's blood sugar varies in response to any number of stimuli, but the most influential is probably food.
So the first test gives you a baseline. By the time of the second test your insulin response should in theory have largely dealt with any rise in blood glucose, and you should be at, or reasonably close to, where you started. That's why the usual target is for the second reading to be less than two points higher than the first one, and not higher than 7.8. If the second readings show higher figures it indicates that your system isn't coping with that level of carb intake, and your blood glucose is being unacceptably elevated.
Implication is there's too much carb in that meal for you to handle, and some at least needs to be removed.
You can also test at one hour, three hours, whatever, if you want to see how you respond. This uses up a lot of strips and there isn't all that much knowledge to be gained.
Many people also test first thing in the morning. This is often the highest reading of the day for many of us. It shows the "fasted" level but also often shows you that your liver is attempting to raise your blood glucose by adding more it's made itself. This can take a long time to stop and come down - I was still getting high morning readings long after I was back in normal HbA1c range.
Personally, given a condition like this, I want as much useful information as possible and I would be aiming for normal levels. Steroids are I believe known to raise BG.