When the graphics on your design are displayed on the Canvas, they are drawn at the resolution specified in the Image Display Quality button at the bottom of the window:

This setting controls how detailed images appear when zoomed in and how quickly the software runs. The recommended setting is 150 dpi. If the software seems to be running slowly, choose a LOWER dpi setting like 72 dpi. If images appear blurry when zoomed in or at a 100% zoom level, then choose a HIGHER dpi setting like 300 dpi. Depending upon the speed of your computer, the 300 dpi setting can slow the software significantly, so use it sparingly.

Note: this setting only affects what you what you see on the screen. When you PRINT or EXPORT a page, the Print Quality setting in the Printing preferences is used. The default Print Quality is 300 dpi.