A website banner

Hi, I need urgently the creation of a Banner advert that will be posted in a magazine website with a lot of audience. They will let me to have it for free as I did a favor before to them but they asked me to provide the banner and code for them.
I am not sure where it should be host if on my site or somewhere else. I need you practical advice to do it fast and efficiently if possible, please.
The banner advert size is 250 pixels h x 316 pixels w
The banner will be to advertise a new book and redirect the people to the website page www.maximokovak.com/books

i HAVE ATTACHED THE PHOTO TO USE AS BANNER

Thanks Paco