Connect changes SSID and other settings to try and connect to the AP you have selected in the scan list. Use Network… I don’t know about that, can’t find anything on the wiki, found only one offhand remark here: http://forum.mikrotik.com/t/wifi-mesh-in-a-rv-park/42672/1
That would be nice… In addition to forums, online manual will be your best friend for learning: http://wiki.mikrotik.com/wiki/Main_Page