Ubuntu – How to install termite

I'm using openbox on UbuntuGnome .. if that helps.

So I reviewed the documentation located here:

https://wiki.archlinux.org/index.php/Termite

and I can't figure out how to install it.
I'm very novice and would just like a simple explanation is possible, or at least a nudge in the right direction.

I also followed the instructions here:
https://github.com/thestinger/termite

Did the following:

git clone --recursive https://github.com/thestinger/termite.git
cd termite && make

then get this:

ask@ubuntu:~/termite$ make
Package gtk+-3.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gtk+-3.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gtk+-3.0' found
Package vte-2.91 was not found in the pkg-config search path.
Perhaps you should add the directory containing `vte-2.91.pc'
to the PKG_CONFIG_PATH environment variable
No package 'vte-2.91' found
Package gtk+-3.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gtk+-3.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gtk+-3.0' found
Package vte-2.91 was not found in the pkg-config search path.
Perhaps you should add the directory containing `vte-2.91.pc'
to the PKG_CONFIG_PATH environment variable
No package 'vte-2.91' found
g++ -std=c++11 -O3 -Wall -Wextra -pedantic -Winit-self -Wshadow -Wformat=2 -Wmissing-declarations -Wstrict-overflow=5 -Wcast-align -Wconversion -Wunused-macros -Wwrite-strings -DNDEBUG -D_POSIX_C_SOURCE=200809L -DTERMITE_VERSION=\"v11\"   -Wno-missing-field-initializers -s -Wl,--as-needed  termite.cc  -o termite
termite.cc:31:21: fatal error: gtk/gtk.h: No such file or directory
compilation terminated.
Makefile:36: recipe for target 'termite' failed
make: *** [termite] Error 1