Using Adobe Illustrator - Creating Symbols 101: Part 1 - Page 2
2. If, like my snowflake, your symbol is white with no outline (or stroke, as it's called in Illustrator), it's a good idea to create a graphic of any color darker than white into your Illustrator, lock the layer it's in, and create and select a new layer, as I did with the sky in my Rudolf the Red-Nosed Reindeer with Lights illustration:
3. Click the symbol in the Symbols palette or Symbols library you want to spray to select it:
4. With the symbol you want to spray still selected in the Symbols palette or Symbols library, click the Symbol Sprayer, next to the Column Graph Tool in the Toolbox. If it's set to another tool, press Shift-S:
5. Click and drag on the graphic you copied/cut and pasted to start spraying!
After you're done spraying, click on any snowflake. A rectangle will appear around all the snowflakes. This is called a symbol set, and each snowflake is a symbol instance.
6. Save your document.
Part 2 will tell you how to edit the symbols you've sprayed.