Welcome to the forum.
Which version of SONAR LE do you have?
Do you have a MIDI keyboard?
Can you read and write music?
The program comes with extensive Help files and should have some tutorials that show you how to put MIDI data (notes) into the tracks and how to set up audio and MIDI tracks for recording.
Some of the tutorials have examples using the TTS-1 software synthesizer, but I think many LE programs don't include TTS-1. A conundrum. You'll need some sort of soft synth to hear the MIDI being played or you'll be stuck using the Microsft GS Wavetable synthesizer that comes with almost every computer in the world that runs Windows.
Open SONAR LE and then click Insert at the top. Go to Soft Synths and tell us which soft synths you have.