Suggest downloading the CBSubs Manual below.

www.joomlapolis.com/downloads/documents

You'll need to create a Tax Rule to apply your tax. This is done within CBSubs > Taxes > Tax Rules. Next you'll need to create your Tax Rate within CBSubs > Taxes > Tax Rates. The Tax Rate will determine how much the tax is and who it applies to.

Europe VAT is complex and the taxing and rates and moreover the numerous exceptions depend on each individual case, in addition the rates and rules can change any time in each country:
ec.europa.eu/taxation_customs/business/vat/eu-vat-rules-topic/vat-rates_en
it's hard for CBSubs to guess any individual situation, so even with all available rates (up to 4 per country), it remains a tedious process to configure EU VAT.

To the best of my knowledge, EU doesn't provide a webservice that lists all VAT rates, and I haven't found a free and up-to-date webservice that could facilitate the setup and maintenance of basic rates. If you have any free and reliable open-data source for all countries VAT rates and rules, I would be happy to look into simplifying the configuration.

EDIT: This is the latest EU's understanding of EU countries VAT rules from January:
ec.europa.eu/taxation_customs/sites/taxation/files/resources/documents/taxation/vat/how_vat_works/rates/vat_rates_en.pdf
It is 119 pages long and should allow every EU business to understand it's position (and maintain it)!
Bureaucracy, politics and KISS (Keep It Simple and Stupid) are 3 different things...
I haven't found an official EU computer-readable version (e.g. JSON or XML), even if just for the "standard" rates!

EDIT2: Even within a country, depending on territory and supplier, VAT rates can change. Unofficial source:
github.com/kdeldycke/vat-rates

Added a FR for collecting information and waiting for official or well-maintained free open-data source:
#7223

And it is called "EU VAT Plugin", because it has the official EU VAT number validation provided by the official EU API.