How do i install a timer my computers in a cyber cafe?

I opened a cyber cafe 2 years 3 months ago. I got someone to install the timers and all the other programs required. But so far I have purchased and had to install more than 10 timers. Am even tempted to think that the person whom I pay to do the job, installs cheap timers so that I continue paying him to install more. Now I have decided to install them my self. My question is, how do I go about it? How do I make sure that I install them properly to ensure that they communicate with the server?
