There are multiple ways from creating your own songs in a daw like FL studio, to just recording you play something in audacity or combine multiple field recordings for an ambient soundtrack. Id say just go out and record anything that you find interesting and youll have an ambient sound rather quickly. If you really want to make your own music you should either get a hand into music theory basics or get a synthesiser of any kind. could be a digital one like vital or serum, or a physical one which you could combine with it like the akai mk3, which is a really decent and rather cheap one.
Hope i could give some new infos, cheers :)