I am going to show you how to use a pattern you have downloaded and use it as a pattern swatch. I am using Adobe CS3, yes I know I am WAY behind, but we make do with what we have. Anyway so we will start with downloading the desired pattern. Just save it to your desktop for easy access. Now let’s open up Illustrator and you can make your document as large as you like.
Mine is 850px by 600px
Once you have your document, drag the pattern you have saved earlier into your document. It should look like this.
Step 2. Now you need to embed your document, to do this click on the ‘Embed’ button.
Step 3. Drag your image into your swatches palette. If you can’t see yours, simply go to ‘Window’ and in your drop down list click ‘Swatches’.
At this point you can delete your image that you dragged into your document.
Step 4. Draw a square (or whichever shape you prefer), and how big you want it
Step 5.Now you can do this next step one of two ways.
1. You can have your shape highlighted; you can click on the pattern swatch.
2. Drag the pattern from your swatch palette into your shape.
And you are done. I hope you have found this helpful. From here you can so much with patterns. Note: to make your pattern bigger or smaller, especially with patterns like polka dots, you can resize your shape before you drop and drag it into to your swatches palette.