Channels are selected by tapping the center button once then using the arrows. The next tap of the center takes you to the CTCSS, DCS, and other functions follow. When scanning simply tap the transmit button and it should stop on the selected channel. Channels 8-14 are FRS channels at 500mw. These are the preferred channels to use for most people. 1-7and 15-22 are considered GMRS and requires a FCC License. Many people have been known to use these channels without having the license. This form of pirating is not recommended. I have included these links which could be of help to you.
To find a PDF Manual for Midland LXT310:
To locate information on obtaining a GMRS license: