Properties
Drawing Properties
Your Properties panel will be your best friend when manipulating your drawing paths.
In this image, I've created two random shapes using the Pen tool.
The shape on the left is a closed path, and the shape on the right is an open path.
The "Fill", "Stroke", and "Opacity" properties will likely be your most commonly used at first.
The "Stroke" of the path determines the color of the lines that you select, and the "Fill determines the color of the inside of the path.
Here I've selected just the diamond shape and changed the fill to red and the stroke to blue.
You can also change the thickness, or lineweight, of the line by adjusting the size. Here I've made both paths on the page have a 3pt lineweight.
By using the direct selection tool, you can click on specific anchor points within the path you've created and individually adjust those.
Here I've selected a few anchor points in these paths and moved them slightly by dragging. In the diamond shape, I have turned the sharp angle on the right into a curve by dragging the white dot on the inside of the angle inward.
You can make a line dashed by selecting that line and then clicking on the word "Stroke" and checking the "Dashed Line" box. You can then change the size of the dashes and the gaps in between.
In order to change the opacity of an object, select it and use the Opacity slider to adjust it on a scale of 0-100.