TeamViewer not working properly on my Desktop

Hi there,
I have this desktop HP pro 3500 Microtower PC, I recently installed TeamViewer 9.0.24482, the package indicated that I will be able to share desktop view, or even control another computer to offer assistance, but nothing is happening on my computer, I have tried uninstalling then having a fresh install, but still its not working, How does this software work, how do firewalls affect its functionality?
