Which model of HP printer is it? If it's an 'all-in-one' printer (as many, but not all, printers are nowadays) it will include a scanner, so that you can achieve what you want. If it's only a basic printer though you'll need to
(a) buy a standalone scanner to go with it ; OR
(b) replace it with an 'all-in-one' model ; OR
(c) find somewhere else that's got a scanner (such as a friend's house, at work, in a public library or at a copy shop).
If your printer has a fold-up lid with a glass plate underneath, similar to an office photocopier (i.e. something like this
https://images-eu.ssl-images-amazon.com/images/G/02/uk-electronics/Stores/Kodak/5250_Small.gif ) then it includes a scanner. Just tell us the model number and we'll tell you how to use it. If there's no fold-up lid then there's almost certainly no scanner built into it.