You'll need a running custom firmware (CFW) such as Atmosphere (most common) or SX OS (older).
On your Switch, select the files from the incoming queue, select your installation location (SD Card is recommended), and confirm the installation. Verifying Update 1.3.2 and DLC Success pokemon shield switch nsp xci dlc update 132 install
Boot your Switch into (e.g., Atmosphere). From the Homebrew Launcher, open one of the following installers: You'll need a running custom firmware (CFW) such
Navigate to the icon on your Switch home menu. Atmosphere). From the Homebrew Launcher