You can install KDE software (KDE Plasma, KDE Applications, and KDE Extragear applications) from both packages and ports. It's a lot faster to install from packages, and compiling KDE software will also take a lot of disk space and memory.
Packages are available from the official FreeBSD package repository.
x11/kf5-frameworks, but each individual framework can be installed separately.
x11/plasma5-plasma, but each individual component can be installed separately.
x11/kde-baseappswhich pulls in the essentials. Each application can be installed individually.
To install KDE packages on supported FreeBSD versions (10.3 and later, and generally x64):
# pkg install x11/kde5 # For the Qt5-based KDE experience