The best way to learn Splunk that I would recommend to you is by enrolling in a paid training with live classes. In this regard, I would recommend you Intellipaat. You can go to its official website and join the Splunk Certification course that they offer. What is different with Intellipaat's course is that they not only offer the best course, but they package it in a way that's the best overall. There are several benefits attached to the course, like Instructor-led course, flexible schedule, 1:1 doubt clearing session, job support, 24*7 technical support and access, Lifetime Free upgrade and access, etc.
To get started, you can rely on free online resources, YouTube videos, documentation, but if you wish to advance in your career or are serious about getting a job after upskilling or wish to make a career transition then this is the best way you choose. As rightly described by Forsang who successfully upgraded his career and has shared his learning experience with us through this video.