How can I start a research?

First you need to build a research center.
When the research center is finished, you can click on it to open it.
There are different categories you can expand to see all the researches. Just click on the research you want to start to see all the details and what benefits you get with it.
If you are sure this is the research you want to do click on the "start research" button, pay the costs and wait until the research is finished.
Only one research can be done in one research center at the same time.