ESP32-S2: Fix readme link, improve instruction clarity

ports/esp32s2/README.md

@@ -30,18 +30,20 @@ Connect these pins using a [USB adapter](https://www.adafruit.com/product/4090)
 
 ## Building and flashing ##
 
-Before building or flashing the ESP32-S2, you must [install the esp-idf](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/index.html). This must be re-done ever time the esp-idf is updated, but not every time you build. Run `cd ports/esp32s2` from `circuitpython/` to move to the esp32s2 port root, and run:
+Before building or flashing the ESP32-S2, you must [install the esp-idf](https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/get-started/index.html). This must be re-done ever time the esp-idf is updated, but not every time you build. Run `cd ports/esp32s2` from `circuitpython/` to move to the esp32s2 port root, and run:
 
 ```
 ./esp-idf/install.sh
 ```
 
-Additionally, any time you open a new bash environment for building or flashing, you must add the esp-idf tools to your path:
+After this initial installation, you must add the esp-idf tools to your path. You must also do this **any time you open a new bash environment for building or flashing**:
 
 ```
 . esp-idf/export.sh
 ```
 
+When Circuitpython updates the ESP-IDF to a new release, you may need to run this installation process again. The exact commands used may also vary based on your bash environment.
+
 Building boards such as the Saola is typically done through `make flash`. The default port is `tty.SLAB_USBtoUART`, which will only work on certain Mac setups. On most machines, both Mac and Linux, you will need to set the port yourself by running `ls /dev/tty.usb*` and selecting the one that only appears when your development board is plugged in. An example make command with the port setting is as follows:
 
 ```