When you have selected a topic for your research project you will first have to familiarize yourself with the topic. You have to get acquainted with the different aspects of the topic, with the terminology and definitions that are used, with theories that are involved, with key authors about the subject. You have to discover how your research topic is discussed in the existing literature in the field.
In the orientation phase handbooks and reference works can be very useful. Handbooks and reference works are designed to give a systematic and comprehensive overview of the accepted knowledge in the field and that is exactly what you need. They even have suggestions for further reading and introduce key publications in the field.
In the University Library reading rooms you will find printed encyclopedias and handbooks etc. The Libguide International Relations on the Library web portal gives a selection of electronic handbooks in the field of IR.
However, be aware that Wikipedia contains both articles of very high quality, and very unreliable information. Adopt a critical attitude and always try to verify the information you have found on Wikipedia by using other information sources.