Canva is a service (started in WA!) that makes it easy to create beautiful slides, flyers, posters, infographics, and photo collages. Start by selecting a template then dragging and dropping into place background designs, pictures, clip art, and text boxes. A video about Canva by Mr Port can be found here.  

Canva has a number of templates to get you started, some of which can be seen below.

Canva also has many free graphics and photos you can use when creating your poster.