You are welcome to create a traditional poster, but if you are feeling inspired, and want to give an online poster a try...check out one of the options below.
Canva makes design simple for everyone. Choose from hundreds of professional templates to create social media graphics, presentations, flyers, posters, invitations and so much more.
Lots of tutorials available available under the "learn" tab in the top left corner of the page.
"Piktochart is a web-based infographic application which allows users without intensive experience as graphic designers to easily create professional-grade infographics using themed templates." You will need to create a free account to use this program. See the tutorial above for more information.