In this article i will show you how to install QT 5.2.1 on lubuntu 14.04, it's actually very easy to do, so you should have no problem.
First of all you need to download the QT sdk installer, make sure you download the one that match with your lubuntu version.
If you are using 32 bit lubuntu then you should get the 32 bit version of QT, and if you have the 64 bit lubuntu then get the 64 bit of QT.
Before we start, make sure you already have C/C++ compiler on your lubuntu, if not then you should run this command:
sudo apt-get install build-essential
Here's how you run the QT sdk installer:
From command prompt/console, give permission to read and execute, like this:
chmod +rx qt-opensource-linux-x86-5.2.1.run
Next you can run the installer, like this:
The QT sdk installation setup wizard should appear, you should know what to do, just click next and next until it finish.