FTPD is an FTP server for Nintendo DS, Nintendo 3DS, Nintendo Switch and Linux allowing you to use an FTP client to transfer files wirelessly with your console.
Select the magnifying glass on the bottom screen, then search for FTPD
Press A while hovering over FTPD from the list of homebrew
Choose .cia to install to the HOME Menu, or .3dsx to install to the Homebrew Launcher
For a graphical user interface choose ftpd
For a text based user interface choose ftpd-classic
Wait until the app finishes installing
Exit Universal-Updater
You can scan one of the QR codes below to download and install the program using FBI. To do this, start FBI, then go to "Remote Install", then "Scan QR Code".