How to use Crop Image code from github in my code

Hi iam newbie to android and i always being confused that how can i use code from github into my app .most of the time i notices that some of the task in our app are beautifully designed by some one in github for example now days iam developing app which need to crop image after selection from gallery and i found this code sample from github Crop Image but i dont know how to use this code in my app, like what is dependencies of that code ,which method can we override to get the result.And also the from Where dose that xml widget appears,and how its made. Below example from same code.

<com.goparties.gpuser.util.CropImageView
    android:id="@+id/cropImageView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@id/toolbar"
    android:layout_marginTop="?attr/actionBarSize"
    android:background="@color/black_trans"
    android:paddingBottom="2dp"
    android:paddingTop="2dp"
    app:cropMode="circle"
    app:frameColor="@color/colorPrimaryDark"
    app:frameStrokeWeight="1dp"
    app:guideColor="@color/orange"
    app:guideShowMode="show_on_touch"
    app:guideStrokeWeight="1dp"
    app:handleColor="@color/orange"
    app:handleShowMode="show_always"
    app:handleSize="8dp"
    app:minFrameSize="100dp"
    app:overlayColor="@color/uncrop_color"
    app:touchPadding="8dp" />

Please give some suggestions how can we use that codes in my app its 2 days now iam looking for way to implement this also the gradle dependencies of above code is missing.