Focusing a macro lens properly is probably the hardest thing about them because the dof is so extremely shallow. One thing I have found very useful is a 4 way macro focusing slider. It allows you to move your camera backwards, forwards and sideways with precision. The one I use is a Neewer and it is around $40 on Amazon. You can pay a lot more but I found this one does the job. The rail also aids in focus stacking, in which you take several photographs at different focus points and blend them in software. This provides a greater depth of field than you could otherwise obtain. Have fun with your new lens Laura. It will open up a whole new world to explore.
Thanks all so much for the great comments and encouragement. I can whole-heartedly assure you that: a) this shot was pure dumb luck; and b) it is cropped to a fare thee well. I will have fun getting to know my new toy though!