Creating a multi language Magento store is really easy, there are a lot of resources out there that will help you both on Magento, and Google.
Basically you need to determine your base (default) language, you have probably already chosen the default locale in system -> configuration -> general -> locale. Under system -> manage stores you need to configure your store views to represent your locales.
Your default store may be in English, so you would create store view for english with a sort order of 0, and then further store views for your other locales, i.e. French.
Now you will be able to switch store views in almost all admin pages to let you add the translated text for products.
You might also find the Magento Connect internationlisation packs helpful for translating common frontend and backend text into your locales.
You can add your own translations by editing the locale .csv files in app/locale. These are very easy to use, open one up and you will see the translations from the Magento default (en) to the locale chosen seperated by a comma. If you edit and save this file you need to refresh the translations cache before you will see any changes.