Click on the "Get Started" button at www.snackfever.com. Select your box and then select which plan you'd like. At checkout, fill in your shipping and billing info, accept our Terms of Service and then click "Checkout".
If you would like to gift a box, select the "This is a gift" option. Gifts do NOT renew by default, but you have the option to have it auto-renew.
p.s. Boxes are shipped monthly but you may pay every month, every 3, 6, or 12 months, just like a magazine subscription :).