In addition to the radical chart, most/all of the Kanji in the Renshuu dictionary indicate the radical they use.
If you click on the hiragana next to the Kanji's radical (which is the name of the radical) it will automatically search for terms with that radical (you can also enter in the name for the radical manually to do this too).
Radicals are " small kanjis" that make up a real kanji. There are 214 radicals as far as I know. Example the radical 氵which is water, makes up water related (or other things) kanjis, example: 池 (meaning pond) you can see the water radical on the left. Hope that helped! 😃☺
