Sarah,
If you have a wireless router, that's the best way to get onto the internet using your phone at home. It's MUCH faster than over the 3G network. It's pretty simple but, if you've never set it up before, it could be confusing.
You need to find your router's manual and follow the instructions on setting up the wireless features. Every router is different and there are tons of websites with step by step instructions. If you have the manual, just follow it. It's too involved for me to type a step by step guide here.
Once you have your router set up to provide wireless access to devices such as your phone, laptops, etc., you then need to go into the Droid X's settings for wireless and turn that on, enter in the name of your wireless network (SSID) and the security info (WPA2 password/passphrase) and connect.
Once it's on you'll see the blue Wi-Fi signal strength meter in your notification bar and the 3G indicator will disappear though the phone network signal strength bar indicators will remain. Then, open a browser and start surfing on the phone. Loading apps from the Market is much faster too.
If you have troubles, just Google your router and read some pages on setting up wireless.
Sorry for not having step by step instructions but you should be able to figure it out.