Underground is the most comfortable and safe kind of transport in Kiev, however, it's quite overcrowded, especially in peak hours. Now you can read the names of Underground stations in English, so, it will be easier for you to locate yourself and the station you need.
Some stations of Kiev Metro were built in the dawn of Soviet era and are decorated in the same style, which is quite unusual and beautiful. Teatralna station was formerly named after the first soviet leader Lenin. Now, is was renamed, but still has a bas-relief of Lenin in bronze and also fragments of his written works also cast in bronze.
The Metro system in Kiev is quite developed, however, is not so difficult, as in Moscow, for example. You can move between central districts of Kiev with the help of the Underground, however, some suburb districts are not covered by it and you should use on-land transport, like bus or trolleybus.
The central stations of Kiev Underground are Krestchatik and Maidan Nezalezhnosti. If you want to see the river Dnieper, you should get off at Poshtova ploscha, which is located in Podil district. Very nice views of left side of Kiev you can see at Arsenalna station (after 10-15 minutes of walking).