I am making a quick project where it shows an image on screen, and you press a button that cycles it to the next photo and so on. I am not very experienced with unity and I am not sure how to go about this. If anyone has any answers they would be much appreciated 
Hey IcePug, try googling the exact thing you posted here. I did and there are like 3 or 4 links that should answer your question. Here is the first one:
Since you are new you probably dont know the forum rules but you really should try to search your question first. Only then should you post in a forum if your attempts dont work. There are also plenty of videos on YT and elsewhere that you can watch to get the basics of buttons and cycle through arrays or lists (for your images in this case).