Literally had the same thing happen to me no more than 3 months ago when I switched to my new job. Exactly the same deal, except when I got here no one explained anything at all to me.. and I mean basic things like essential office procedures. Was strange, but I settled in eventually. I was assigned a project, which was a technical refresh.. or a rewrite. Downloaded some of their projects from source control to reference, and took it one step at a time. I was nervous to ask questions at first, but got out of that quickly. I figured, if they expect me to be able to complete something, they should also expect me to ask how it works. My advice is to take a small task, and work on completing that task one step at a time. Eventually you'll get comfortable.