I need some help applying for a Schengen visa. We want a tourist visa. How to apply for a visa and what documents are required for that?
First you need to identify the consulate responsible for your place of residence. I could not find a page from the Portuguese ministry of foreign affairs that would help with this, so a web search is probably your best bet.
Then you should find the web site of that consulate. There should be a link for "visas" on the main page. It may be hidden under a link for "consular services" or something like that.
Following the link, you should find instructions about how to apply for a visa. You will probably be redirected to a third-party service provider that is responsible for accepting the application, in which case you should visit their site and follow the instructions there as well.
Without knowing where you reside, it is not possible to offer a more specific answer, but this general outline should be helpful nonetheless.