Poppler is a PDF rendering library based on the xpdf-3.0 code base. I have already downloaded the tar.xz file from the official site http://poppler.freedesktop.org/ But I do not know what to do with this file
Is there any command to install or run?
P.S. - I am new to linux, so I don't know a lot about it yet..
What you downloaded from poppler site is source code and you may not be expert enough to install it yourself. For such situations, Ubuntu and other linux distros manage packages of popular software so you don't have to go through manual installation via source code. In your case, poppler for python is available in package python-poppler which can be installed via Ubuntu's package manager apt.
To install poppler python bindings open terminal and run this:
sudo apt-get install python-poppler
You should have poppler available in python then.
To search for such packages in future you can do apt-cache search poppler. It will list down all packages you can install via apt.