That's a broad question. There's a lot to it and I'm still learning myself. I would recommend logging into SplunkBase and downloading the app "UI Examples". I think you'll find that very helpful.
You can also check out the module reference in the Splunk docs here.
It really just takes some practice and trial and error.
If/when you have more specific questions there are people on here who can and will help you.
Hope this helps!
