You're gonna need a DAW (Digital Audio Workstation) to really start making music.
There's plenty to pick from, all do the same things in different ways. Every DAW is also gonna come with it's own set of synths, effects, etc.. but you can download other synths/effects that work in all DAWs.
I use FL Studio (which is fairly cheap for the highest version, and you get free updates for life, and comes with great synths, but it's PC only), but there's Ableton Live, Logic (MAC only), Cubase, Reason, and Reaper (Reaper is only $50 for a non-commercial license, however the demo is full featured and there is no time limit on it. It doesn't really come with any synths though, but loads of FX.) There's more than that but those are the big ones that come to mind.
Again, don't bother searching for which DAW is best because everyone is gonna be biased, and they are do the same thing, just how it's done is different.
Just try out the demos and see which one you like the most!
After that, get ready for months of learning your DAW inside and out..
