Knowledgebase
How to add custom options to products in Magento
Magento has settings which you can use to create custom options for any of the products in your catalog. You can use this to offer a product in different variants (e.g. based on color, size, etc.). The same things can be achieved with configurable products. The choice which to use depends on the particular product and options that you want to offer to customers. The chief difference is that with configurable products the inventory of each product variation is managed separately. This is not the case with a product with custom options.
To add custom options to a product, log in to the admin panel, go to Catalog>Manage Products and select the product that you want to edit (or click on the Add Product button if you want to add a new one). When you get to the page with the product settings click on the Custom Options button on the left. Then click on the Add New Option button on the right.
You have to type a name for the option in the corresponding field, then select an input type and choose whether the option should be required or not. After you select the input type some more settings will be display. Type an SKU in the respective field (you can use the name of the option). You can use the price options to configure whether the cost of the variant should differ from that of the basic product. Depending on the input type that you selected there can be some specific options such as one for the maximum number of characters (for text input types). After you're ready with the settings click on the Save or on the Save and Continue Edit button.
For more details and screenshots you can also check out the tutorial on custom product options in Magento.