Mountain Climbing with friends

I am not a sporty type of person and don't expect me to do some big adventures as well. During our travels, we usually go to kid- friendly resorts where they can enjoy some beach and outdoor play. I never did something really hardcore like mountain climbing. But two weeks ago, my friends invited me to join them in mountain climbing. I have seen their previous photos already and they were all beautiful. The problem is I am really scared since this will be my first time. They promised to help me out all the way, including buying the Deuter Act Lite. I need a backpack for all my clothes, food etc. I have to admit that I feel excited but somehow a part of me is still nervous. Oh well, just wish me luck!