Assuming you would like tips on how to draw using the Preview app on a Mac:
1. Open up the Preview app and choose the file type you’d like to create. For example, select “New from Clipboard” if you want to create a new file based on an image copied to your clipboard.
2. If starting with a blank canvas, choose the size and shape of your drawing area by selecting “Custom Size” under the New File drop-down menu. Enter your desired dimensions in pixels or inches and click “OK” when finished.
3. To add color or shading to your drawing, select the appropriate tool from the Toolbox located at the top of the window (the icon looks like a pencil). Then, use your mouse or trackpad to click and drag within the drawing area to start drawing.
4. To save your work, go to File > Save As… and give your file a name before clicking “Save”.