How to accustom myself to my boyfriend's size?

Kathleen • I am 18 and going to college to get a bachelor`s in biology. I will then go on to get my DVM. Im engaged to the love of my life. I love to sew, and create. I love birds, they are lovely.
So I wanted to try my first time in case it would not fit. We tried and it did not fit. I think its a combo of me not being wet enough and us not having lube. Any other ways to help this, and help me become accustomed to the size he is? Thank you.