A wide variety of options are available to you design your poster. The two main options open to you are using a template and simply adding your data and text to the design OR designing your own.
If you are using the free version of Canva (highly encouraged) you will have to click through their introduction pages each time you enter the site to create or revise your infographic.
You'll begin by speciifying your design size. You are not able to change the design dimensions once you've started while using the free version, this was the thing that I was most frustrated by. So make sure you have the width and height in the correct blanks as your first step. If you're creating a poster to use for a trifold the dimensions should be 36 inches in height and 48 inches in width.
There are tons of free options here for you to create virtually anything at absolutely no cost. They do also offer graphics, fonts, icons, backgrounds for a small fee if you just don't see enough options!
You can even upload your own images and charts, such as ones you might create using Microsoft Excel, to use as a part of your infographic. Once you have the graphic placed on your infographic, you can then delete it from the upload screen. Because you are using the free version, it really slows down the response time and you only have space to add one or two items to the uploads. However, once it's on your infographic, deleting it from the uploads has no impact on whether or not it continues to appear on your infographic.
This was my favorite program to use to create inforgraphics. I really felt that I was able to be much more creative and there were just so many more choices available to me. I was even able to decrease the spacing between letters and lines of text, which had a better look for what I was trying to accomplish. Also, the variety of colors was incredible and I could easily lighten and darken the texts by making them more and less transparent to ensure my colors were in the same color group. One of my favorite parts of the design features was the ability to center and make sure that things were straight and lined up on my page. It uses the center of whatever object you're moving to line things up, so even if you're moving pictures, text blocks, or whatever, you can easily make sure it's all lined up and has an eye-pleasing impact.
This program is probably the easiest of the three shown on this page, but also has the most limited options for graphics and icons. However, if you struggle with creativity or want something that is very straightforward to use, this is what you'll want to use.
As soon as you click on a size for the poster that you want to create, 36x48 for trifolds, you will have several different templates to choose from. The templates are based in Powerpoint, so upon selecting a template, it will open Powerpoint on the computer or device you are using.
The templates are very similar in set-up and mostly varies in color. Once you have the template open, you simply begin inserting your data, text and images until you have filled up the poster.
These poster templates are probably the easiest ones to use in order to create your infographic. The template is designed as a "fill in the blank" type solution, which makes creating it a lot less time consuming than either Canva or Easel.ly.
This is also a great option to use if you are working in a group. Once you have saved the file in Powerpoint, you can use Google Docs to share access to the file, make changes and update with your group.