Many Scenario Sketch Tools functions call for you to edit the map and select particular features.
To edit the map and select features:
1. Use the Scenario 360 Start
Scenario Editing 
button if you are working on
a dynamic layer, and use the Start Editing
command from the ArcMap Editor menu if you are working on a non-dynamic
(reference) layer
2. Make the layer you are working on selectable (preferably the only selectable layer) using ArcMap Selection tools
a. From the ArcMap main menu, choose Selection > Set Selectable Layers…,
-OR-
b. Use the Selection tab at the bottom of the Table of Contents
3. Make sure the ArcMap Editor is in Select
Mode (with the arrow 
cursor showing)
4. To select one feature, click on it once. To select multiple features, hold down the Shift key while clicking, or drag a rectangle over multiple features. The selected feature should become highlighted on the map.
5. Instead of clicking on the map, you can select a feature(s) by clicking on its row(s) in the layer attribute table.
Scenario Sketch tools that are applying attributes to a layer also require that the editing Target layer be set to that layer. To set the Target layer:
1. Start editing
2. In the ArcMap Editor toolbar, choose the layer from the Target: drop-down list.
3. If the Target drop-down list is not showing,
click the Target 
icon.