Everything you place on the canvas is an element. Add elements from the Toolbar, then style the selected one in the Property Panel.
Images
You need to upload images to your image library first, before you can add them as image elements to the canvas. Select the image tool to access your image library and then click Upload to add a new file. Then select the image from the library to create a new element. Images have properties for how they fill their bounding box and which point they anchor to. See Cover mode and Origin.
Text
Add a text element and type your content. Text can anchor from different points, wrap across lines, and follow a curve. Text always resizes to fit; it will never overflow out of the bounding box. See Origin, Wrap, Font size, and Curved text.
Rectangle
Draw a rectangle with the shape tool, then set its size and fill in the Property Panel.
Ellipse
Draw an ellipse (a circle or oval) with the shape tool, then set its size and fill in the Property Panel.
Path
Draw a custom vector shape with the path tool, placing points to form lines, curves, and freeform outlines. Edit the points afterwards to refine the shape.
Groups & Masks
To combine elements, you can group several together or mask one with another.