Secret of Doing: This last, above, is the template I used to make the above posters. It is in Mac's Pages (Word for PC users). I double clicked on each image above and then used the paste command to put my own pictures inside those image shapes. They popped right into them. Likewise for the words, I typed my own words over the ones shown. For all but two of these, I followed the template very closely. I got into trouble with the way Women's Suffrage and Leopold & Loeb looked so I had to paste new items over existing ones in Pixelmator (Photoshop clone) to fix them. If you have art talent, do the same. If not, don't do it. Instead, start making a new poster with the template again but using better pictures. You may be satisfied right at this point where all your pictures and words are in you poster. You can go ahead and print your poster in Pages or Word.
However, I wanted more versatility so I went further. Most file menus in most programs give you the option to export your file into another format, so you can use it in other programs. So the next thing I did was export the file into pdf format from Pages. Once it was in pdf format, I opened the file in Pixelmator. I then converted it to a tiff file in Pixelmator, suitable for making posters, and into jpg files, which are suitable for posting on the web (here). I made the posters for Teachers Pay Teachers here. Pages is a free program on Macs but Pixelmator cost me $29 (a bargain but GIMP is free and also works).
You probably need Intermediate computer ability to do what I've described here. If you are a Beginning Level computer user, this will be too much for you. But you may have a child or grandchild around who can follow these instructions like a whiz so can try that option instead.