Q: I am an 18 year old female and have never seen a penis.  What do they look like?

 A:    All penises look a bit different, but in general they are long fleshy rods, that are soft and floppy when limp, and harder and upwards pointing when erect. (Think about a muscle that is loose versus one that is being flexed.)  Penises are much smaller when they are limp, and when they are erect they are generally between 5 and 6 cinches.
Some guys have circumcised penises, which means that the tip of the penis will be shaped almost like there is a little helmet on the last inch or so of the penis.  Guys who are uncircumcised will have penises that are shaped more like a carrot.
If you’re really curious about what a penis looks like, I would google the word “penis” in google images.  Otherwise, you can go to your local library or bookstore and look at any guys’ puberty book.  That will be sure to have a picture of a penis.  If you’re embarrassed, you can always say that you’re picking up a puberty book for your younger brother, and just wanted to see what topics were covered.