How to create a custom template for a custom taxonomy?

Templates

See the Template Hiearchy for a more detailed break down of how WordPress chooses the template.

For a taxonomy term slug (‘monitors’ your example) in the taxonomy taxonomy (e.g. ‘products’) WordPress will try to use the following templates (in this order)

taxonomy-{taxonomy}-{slug}.php
taxonomy-{taxonomy}.php
taxonomy.php
archive.php
index.php

For your ‘monitors’ taxonomy term page, WordPress will use

taxonomy-products-monitors.php

if it exists. If it doesn’t, then for that taxonomy it will fallback to

taxonomy-products.php

and so on.

Permalinks

The following url should point to the ‘monitors’ products page:

 www.example.com?products=monitors

You have also specified an url rewrite, so assuming the rewrite rules have been flushed and there isn’t a clash, the following should also work

 www.example.com/products-category/monitors