We need to add the implementation com.square.picasso.picasso:2.71828 in the build.gradle dependencies. Version 2.71828 is the latest at the time of writing. To make sure we use the latest version, it is prudent to check http://square.github.io/picasso/ and use the latest version in the Gradle dependencies.

We need to add the following line in the dependencies section of the build.gradle file to have Picasso available for our app:

implementation com.squareup.picasso:picasso:2.71828 

The modified build.gradle file should look like the one shown here:

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'com.squareup.picasso:picasso:2.71828'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}