Once Power Select is installed a new menu icon will appear in the tool shelf. Press it to activate Power Select. Note that there is only one Power Select tool in the tool shelf. Power Select aims to handle switching of selection methods contextually removing the need to manually change selection methods most of the time.
Options (A): Open Power Select’s options menu.
Tweak Mode (B): Set the tweak mode (Tweak, Drag, or Smart). Power Select adds the ability for Blender to record individual tweak settings for vertex, edge, and face modes. This means Blender will remember your different tweak settings when switching between vertex, edge, or face selection modes.
Shift Select Mode (C): Enabling this option will cause box/lasso selections to subtract from the active selection rather than add to it.
Create Group (D): Press the plus button to create whatever kind of group makes the most sense for whatever you have selected. For instance, while in Object Mode this creates a collection of all selected objects. Pressing it while in Mesh Edit Mode creates and assigns a vertex group from the selected mesh. Pressing it while in GPencil Mode creates a layer from the selected points. Pressing it while in Pose or Armature Edit Modes creates bone groups from selected bones. Hold Shift before clicking the plus sign to name the new group before creating it.
Radius (E): This controls the brush size when drag (circle) selecting.