Community Tip - When posting, your subject should be specific and summarize your question. Here are some additional tips on asking a great question. X
I use symmetry all the time.......on the flyout if you choose symmetry constraint, you click the centerline (you have to use the centerline command in the lines flyout), then the two objects you want to make symmetric, such as circle centers, and they will snap symmetric.
Here is a video for you....