BottomAppBar item on right side

you need to add bottombar with fab as below in your xml

<com.google.android.material.bottomappbar.BottomAppBar
      android:id="@+id/bar"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_gravity="bottom"
      app:fabAlignmentMode="center"
      app:fabAttached="true"
      app:navigationIcon="@drawable/ic_menu_24"/>

  <com.google.android.material.floatingactionbutton.FloatingActionButton
      android:id="@+id/fab"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      app:layout_anchor="@id/bar"/>

also check this tutorial if you want to know how to setup your bottomappbar