Could my teenager have autism?

I’ve had suspicions for a little while now that my 13 year old daughter could have autism. But how can I tell the difference between if she’s just a typical type teenager or not? She has always struggled fitting in with peers, she struggles with school work, she doesn’t always compute things as easily as anyone else would, she also has social anxiety. To name a few. What are the signs? How can I tell? What is the very first step in getting an assessment? Any advice appreciated.