Sorry... but no such "pre-Master's language learning year" programmes really exist... when you apply for a Master's course, you will need to be pretty fluent in the language in question (Finnish or English) already. See e.g.
http://www.universityadmissions.fi for instructions on how to apply.
You could, of course, take part in short-term Finnish courses at summer universities -
http://www.kesayliopistot.fi - an ordinary "tourist" visa would suffice - but it is usually not possible to get a (student) residence permit, which you'd need if your stay in Finland was longer than three months, based on language courses only. Generally, you can only get such a student residence permit if you are accepted into a
degree programme at some Finnish university.
To be honest it's not a realistic idea to "learn Finnish" in
one year to such a level that one could be accepted to a Finnish-language Master's programme - unless you are a linguistic genius. If your Finnish skills are zero at the moment, even after a year of full-time studies, attending university lectures in Finnish might be a bit like as if you had been beamed up to a zhnok-walloping academy on the planet Neptune.
And it's nearly as cold here, too
If you're admitted to an English-language Master's programme, however, then you can also take Finnish language classes at the university's language centre so as to learn a bit of Finnish to help you in your everyday life here.
