You would be astonished how many times people call me to ask where their advert is going or why a newspaper has changed/cut their copy.
An advert is paid-for. You contact the paper, tell them what you want to say and pay them to print it exactly as you wish.
A press release is a story that you submit to the paper in the hope they will run it for free. The pay off, of course, is that while this will be free if they cover it, you can’t guarantee if they will use it, let alone where or when.
Not confusing the two will make life easier. Much like the advice a weary flight attendant gave me to help me tell the difference between the "call attendant" button and the light bulb one.