I am using ArcGIS Desktop for the first time in many years.
I have a postal sector layer under a series of merged drive time boundaries.
How do I select just those postal sectors which fit within the drive time boundaries?
You could use the Using Select By Location)
The Select By Location tool lets you select features based on their location relative to features in another layer. For instance, if you want to know how many homes were affected by a recent flood, you could select all the homes that fall within the flood boundary.
Click Selection > Select By Location to open the Select by Location dialog box.
Choose the type of selection that you want to make. Click the drop-down arrow to see your choices.
Identify the target layer(s) from which features will be selected and check them on (Display). Choose the spatial relationship rule that will be used for selection.
Specify the source layer that will be used to select features from the target layer. Setting the source layer for Select By Location