Using pkg-devel port

[Jamie Griffin]

I would like to use pkg-devel on my FreeBSD 10 Stable system. The current
version is 1.2.7_4.

Do I need to remove that first and build the port or will building and
installing the port automatically change the necessary components?

When I ran the make install earlier I got a 'stop' stating WITH_PKGNG is
not defined to 'devel', this version is the devel one. I don't have any pkg
related variables set in /etc/make.conf currently so, should I define that
one and possibly any others before trying again?

Many thanks, Jamie