I've recently written a beginner's article explaining what partial classes are and how to use them. My Partial Classes Tutorial walks you through how how partial classes work, how to create partial classes, when one would use partial classes, and a few other bits of useful information. If you don't know much about partial classes I recommend you read the article it has some useful information in it. If you have any partial class question either ask me here or comment on the article. I will be happy to answer questions.
As always, thank you very much for reading.