The Splunk website has a landing page with links to a vast array of additional information on configuring and using Splunk: https://www.splunk.com/en_us/community.html.
Some of the more useful of these sources include the following:
Splunk documentation is, as you might expect, an extensive collection of documentation and tutorials that covers all aspects of all of Splunk's products. In the Splunk Enterprise documentation landing page, for example, you'll find tabs for Get started, Search and report, Administer, and so on with links to manuals for related topics. The Admin Manual and Getting Data In manuals under the Administer tab are particularly useful for administering Splunk.
Splunk answers is a collection of questions posted by Splunk users and administrators with answers provided by experts in the field who have solved those particular problems. If you use a search engine such as Google to look for an answer to an issue working with Splunk, here or in Splunk Docs is usually where you'll end up.
Splunk education offers a number of Learning Paths for users, Splunk administrators, architects, developers, and so on, which I highly recommend. While this Quick Start Guide is intended to introduce and guide you through the most important and useful features of Splunk from one source, and provide some practical experience and examples of common configurations and challenges you'll encounter, you will want to pursue a formal education path if you wish to obtain a deeper understanding of Splunk and achieve the various levels of Splunk certifications such as Certified User, Power User, Admin, Architect, or Developer.
I also recommend that you download, print, and peruse the Splunk Quick Reference Guide: https://www.splunk.com/pdfs/solution-guides/splunk-quick-reference-guide.pdf.
This is an excellent resource both to accompany the chapters that follow and to keep by your side as you perform day-to-day Splunk administration tasks, as it covers the most significant concepts and information about Splunk as well as a great deal of reference material that is helpful for performing searches using the Search Processing Language.