1. Create a folder called 'libs' under your apps directory in Android studio for your project.
2. Add the jar file.

3. in your build.gradle file:

   dependencies {
     compile files ('libs/commons-io-2.4.jar')
   
   }
   

EDIT: here is what your directory structure should look like:

I was having same issue then realized that the version of commons-io getting picked up was lower than what I need (2.4)....I need to Override the already managed version as below to get the right one picked up:

<dependency>
     <groupId>commons-io</groupId>
     <artifactId>commons-io</artifactId>
     <version>2.4</version>
 </dependency>