I'm using Unity 5 to make a small game (I'm a beginner) and I want to make a 3D model of a character. I'm not sure what software there is to do this and if there is some, I would like it to be preferably free, but if anyone can help or give advice I would appreciate it. I want to be able to make a 3D model and then import it to Unity 5. Thank you.
Blender likely meets your requirements. I have used it in the past to make 3D models and export to model files which Unity can import.
I would highly recommend watching some tutorial videos before using it:
Blender StackExchange can help answer more questions about Blender.