Hi there, as Scott mentions being able to recognise intervals and what notes sound good together is an excellent place to start.
Try playing happy birthday, the intro to your favourite TV programme or even commercials, you'll soon start to notice how often certain intervals crop up time after time, when you can play little tunes in one position move them around to different strings and different positions on the neck.
Find how many ways you can play a CMajor scale, hum or sing a tune then find the notes on the bass, with your ears and fingers working together you'll soon be able to noodle around like your mate. Hope this helps and best of luck