Try using the focus, up your gain and brightness to the max until focused then back them off to show detail
You shouldn't need an extension though if you do you can unscrew the front of a barlow and use the body as one. Find a very bright star or plantet like Jupiter or Saturn or moon, it will look like a faint doughnut till you have it focused. Having the gain and brightness all the way up and the longest exposure possible will help with first finding something to focus on like a planet or star.
Also please use the beginners section as this section is reserved more much more complex issues and discussion of equipment. You can also use the search feature of the forum to see if this question already has a thread and answer.