In here you will get several new building tools which you can access if you purchase credits. You can also earn credits by making cool songs, instruments and dsp chains, but this process always will be slower than just directly swipe out your credit card.
You need to gain XP to extent the building area and to gain this XP you are required to accomplish these missions for creation of instruments, DSP chains and songs.
The higher the level, the more XP you need to raise the level thus also the area to be able to add building tools and the unlocking of new building tools.