How do I lock my Dell TruMobile 2300 wireless router to keep the neighbors from getting access to my wireless internet connection

Press win key + r
under run type cmd
on the command prompt type ipconfig
not down your defaut gateway.
type it in your web browser, and then enter the correct user name and password for the router.(i u dont know the user name leave it blank or try admin for both user name and password or its combination o call dell for it)
Create a unique password on your router : Once you have logged into your router, the first thing you should do to secure your network is to change the default password* of the router to something more secure.
This will prevent others from accessing the router and you can easily maintain the security settings that you want. You can change the password from the Administration settings on your router’s settings page. The default values are generally admin / password.
Change your Network’s SSID name:
The SSID (or Wireless Network Name) of your Wireless Router is usually pre-defined as "default" or is set as the brand name of the router (e.g., linksys). Although this will not make your network inherently* more secure, changing the SSID name of your network is a good idea as it will make it more obvious for others to know which network they are connecting to.
This setting is usually under the basic wireless settings in your router’s settings page. Once this is set, you will always be sure that you are connecting to the correct Wireless network even if there are multiple wireless networks in your area. Don’t use your name, home address or other personal information in the SSID name.
This is sufficient to secure your router from other to use it.