It depends on what you want to get out of it, how much/what kinds of relevant experience you have, and how advanced you want to get into it.
First off, if you don't have at least some basic programming experience with a relevant (or similar enough) programming language, I would recommend doing that first. Struggling with both the language/programming basics and the device-specific interface or libraries all at once is asking for a painful experience. So look up a simple tutorial for Java/C#/etc first if you don't have such an experience. What language exactly, will depend on what your next plan is.
Ideally, get at least some basic experience on game programming too (not mobile game specific), to get familiarity with game engine basics like drawing, game update loops, etc., that'll also help understanding the process later on.
Second, for Android-specific matters, there are a few different ways to go. I'm not listing them all, but here are a few relevant and practical options:
A) Get
Android Studio and SDK Tools. This is the official app development suite, which can also be used for game development. It allows a lot of flexibility and has exhaustive libraries for basically everything that an Android phone or tablet can do. However, it's probably harder to get something going with it than with option B.
B) Use a game engine such as
Unity3D that can deploy to Android (will also require the Android SDK tools). This is probably the simpler option for someone with less programming experience, and allows you to focus more on the game development part than on mobile or Android specifics - you can just develop a game normally on PC, and then worry about the deployment to phone/tablet part later. Unity3D can use C#, JavaScript, or Boo - in practice I find C# is used in the (vast) majority of cases, so it's easiest to find help for that. I would recommend this if you don't have significant programming experience (and probably just in general, for that matter).
Pick up your tools of choice outlined above, read up on tutorials and documentation about it, then just try to get going! See how long it takes for you to get stuck at something, try to find a solution for it, and repeat. Eventually it'll get somewhere.
As for documentation links, you can easily find them for whatever specific software or programming language you're using in question (just google 'X documentation' where X is the tool or language in question, add more specific queries as necessary). Tutorials, likewise. Look for official guides from the software's or language's developer's site in particular.
