I am not able to access django inside virtual environment
Any virtual environment starts out essentially blank, with no packages installed, so you will have to install Django again in the environment.
Part of the reasoning for this is because if you install something with pip outside of a virtual environment, there's a chance that another python package or program somewhere might break -- this can be from namespace pollution (installing multiple modules that are imported in the same way but work differently) or having different versions of the software (an update breaks some functionality that something else relies on). Even if Django itself doesn't break anything, some dependency it has might be able to.
Another advantage is that you can always run pip freeze > requirements.txt in your environment to list all installed packages and versions, then pip install -r requirements.txt in another environment. This makes package import and versioning effortless when you move among development machines or between development and production, and helpful if you'd ever like to roll your own package.
If I install django on local system, then that django, if I access in virtual environment, will that be accessible, or I have to install django again in VirtualEnvironment?