You can leave those unconnected unless you use them (Those pins are GPIOs, but are labeled as TX,RX, etc. as those peripheral components are fixed to the corresponding pins for functionality and use I believe)
Like hima stated, if they are GPIOs you don't need to do anything with them; If they are pins that are explicitly called out to be wired to ground or voltage reference, then you will want to wire it as specified. Otherwise, the default state for unused pins (pins not explicitly called out to be connected to wires) is to be unconnected.
