I am sorry my testcase uses Qt, but it would be much more time consuming for me
to learn/rewrite everything without Qt.

This is the qmake file:
# cat fbotest.pro 
QT       += core gui opengl
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = fbotest
TEMPLATE = app
SOURCES += fbotest.cpp
HEADERS += fbotest.h

Then run qmake, make, ./fbotest

The testcase draws a rectangle and some text into a FBO, then blits it onto
another FBO due to multisampling, finally draws the texture on screen. This is
common practice.

Thank you for taking your time to try the testcase!