Welcome to X-Cart! Please start by reading the forum rules, and posting your X-Cart version in your signature (Edit profile, enter version, enter password, save):
http://forum.x-cart.com/viewtopic.php?t=6489
Next, try the manual, found here:
http://www.x-cart.com/xcart_manual/compiled/X-Cart_4xx_manual.pdf
If you still have questions after reading the manual, please search the forum first, as many of the most common questions have been answered multiple times. If you still can't find the answer, post a question.