Text from: https://docs.derivative.ca/Category:Python
Installing Custom Python Packages
Part of the great power of Python is its access to the countless number of modules that have been created. If you want to use modules that are not included in the above, use the following steps: Install a parallel copy of the same version of Python to the hard disk. The current version of Python shipped with TouchDesigner is 3.7.

Install the package to the parallel python installation, following its normal installation procedure. Launch Python and import the module manually to make sure there are no errors. Once the module is successfully installed, it will automatically be visible in TouchDesigner by default. This option is found under the Edit->Preferences menu as “Add External Python to Search Path”.

Alternatively you can add the search path by modifying the Preference labelled “Python 32/64 bit Module Path”. Multiple paths are separated by semicolons (;). Finally you can modify the search path directly by either modifying the system environment variable PYTHONPATH or by executing a script which appends the path to sys.path as in the example below.

import sys
mypath = “C:/Python37/Lib/site-packages”
if mypath not in sys.path:
sys.path.append(mypath)

Examples of other useful Python modules are here. Unofficial precompiled modules found on Christoph Gohlke’s website. Check the link below
https://www.youtube.com/watch?v=KXFm7CuSK_w