You can connect a music keyboard to your computer to play and record the software instruments built into Logic Pro. You also need to add a software instrument track and choose a sound.
Do one of the following:
If the keyboard is a USB music keyboard, connect the USB cable from the keyboard to your computer.
If the keyboard is a standard MIDI keyboard, connect the keyboard to a MIDI interface using standard MIDI cables, then connect the MIDI interface to your computer.
If the keyboard is a Bluetooth or Wifi music keyboard, consult its documentation for instructions on how to pair it to your computer.
Be sure to follow the instructions that came with the keyboard, which may include installing the correct driver on your computer. Check the manufacturer’s website for the latest driver software. If you’re using a MIDI interface, be sure to follow the instructions that came with the interface.
Do one of the following:
Choose Track > New Instrument Track. (If you use this method, you can skip steps 2 and 3.)
Choose Track > New Tracks.
Click the Add Tracks button 
above the track headers.
In the New Tracks dialog, select Software Instrument & MIDI, and make sure that An Instrument Plug-in is chosen as the input source from the Input pop-up menu. You may also choose a software instrument from the Instrument pop-up menu.
If you have Show Advanced Tools selected in Advanced preferences, the New Tracks dialog differs from the one above. In this New Tracks dialog, click the Software Instrument button. You may also choose a software instrument from the Instrument pop-up menu.
Click Create.
In the Library, select a patch category from the list on the left, then select the patch you want to use from the list on the right. If you’ve already chosen a software instrument for the track, the software instrument may change depending on the patch you select.