This is a great comprehensive tutorial to see what Canva offers to help you in your design journey.
From uploading & cropping images to adding frames and texts, as well as explaining layers and photo positions in detail; this tutorial will help you design just about anything!
Step 1. Click on "Create a Design" on top left corner
Step 2. Click on "Custom Size" to set up the size of your poster
Step 3. It's VERY important to change the unit of measurement first from px (pixel) to in before you enter the desired size
*if you put in the dimensions before changing the PX unit to IN, it will simply convert 24 x 36 pixel to INCH which will not make an accurate 24" x 36" poster*
Once you enter the desired poster size, click on "Create New Design" and you're set to start designing your poster!
Step 1. Click "Share" on top right corner
Step 2. Change file type from the dropdown menu to "PDF PRINT" and click "Download"