The following source is a detailed guide to using PowerPoint to create your poster.
University of Stirling. (2010). Guide to creating academic posters using Microsoft PowerPoint 2010. https://www.stir.ac.uk/media/stirling/services/internal/is/documents/CreatingAcademicPostersUsingPowerPoint.pdf
Poster Basics from the NYU.edu website has some great ideas and links for software and images.
This article explains how to make an academic poster:
Gundogan, B., Koshi, K., Kurar, l., and Whithurst, K. (2016) How to make and academic poster. Annals of Medicine and Surgery. 11(69-71). https://doi.org/10.1016/j.amsu.2016.09.001