Follow the link here and select the appropriate download option for your computer: https://www.ti.com/tool/download/SIMPLELINK-MSP432-SDK/3.40.01.02. Then run the installer and click "Next". You should see a window similar to the one below.
You may specify an installation location here, but we recommend using the default installation path by simply clicking "Next". Nonetheless, make a note of the Installation Directory you use. You will need it again later. Follow the rest of the instructions until you have finished installing the SDK.
The next step is to register this SDK in Code Composer Studio (CCS). Open CCS. Go to the top toolbar and Window -> Preferences.
You should see the screen below.
Click on the dropdown arrow next to "Code Composer Studio", then choose "Products". You should see the screen below. In "Product discovery path" box, you should see the directory you installed the SDK to (by default, this is C:/ti, which is shown below). If you do not see your installation directory, click "Add..." and choose the folder where your SDK is installed to.
Click the Refresh button so CCS can search for the SDK. Follow any prompts that appear including "Install". You should now see "SimpleLink MSP432P4 SDK" in the "Discovered products:" box, which means you are done!