Hello Christie
The memory usage view is in [Image Info>Memory usage]
[example photo]

For monitor in run time, Are you referring to monitor heap and stack usage?
The Heap and Stack View offers the ability to monitor heap and stack usage within their
allocated regions of memory. The View allows the monitoring of heap usage in real time.
This section appears in a window in the bottom right or can be added in Window tab>Show view>other>Heap and Stack Usage
For more information please refer to MCUXpresso IDE User Guide
Chapter 20.6.1 Memory Usage
Chapter14.12 Heap and Stack view
Best Regards, Luis