My (17M) girlfriend (16M) wants to give me a blowjob and I don’t know what to do

So title pretty much sums it up. I was driving her home last night because we went on a date and we’ve been dating for a week. First we were talking about kissing then it went towards sex. I’m a virgin and she isn’t. She asked if I had ever received a blowjob, I said no. She then volunteered to give me one. I politely refused and said, “maybe sometime deeper in our relationship”. Now it’s on my mind and I really like her and I don’t want her to think that I don’t because I turned down a bj. I’m also really nervous about it and don’t know where we would do it. Any advice would be appreciated, thank you