Where to make content?

Hi, I was wondering where you make all the content wich is buyable on the marketplace in UE 4? like how do you make different material packs, gun packs, sound packs, character packs, light packs and etc.?

you make content in 3rd party software, for example you make models in a modelling app like blender/max/maya and make textures in photoshop/gimp, after you make the assets bring them into UE4 to put them together.

hope that helps:)