Learn Finnish: Hankimme omakotitalon viime vuonna. - We acquired a detached house last year.

It is the total object of the sentence. Because the action is complete—we acquired the entire house—the object takes the genitive-like accusative ending -n.

Does hankimme mean 'we acquire' or 'we acquired'?

In this sentence, it means 'we acquired' (past tense), but it looks exactly the same as the present tense! For verbs ending in -ia or -iä like hankkia, the past tense marker -i- blends in, making the present and past forms of the 'we' form identical. We know it is past tense here because of the time phrase viime vuonna (last year).

If I wanted to add a location (like 'in Espoo'), how does the verb hankkia behave based on this lesson's theme?

Just like ostaa (to buy) and löytää (to find), the verb hankkia requires a 'from' case (the elative -sta/-stä or ablative -lta/-ltä) when mentioning a location. Even though you acquired it in Espoo, in Finnish you acquire it from Espoo: Hankimme omakotitalon Espoosta.

Why is the word for year (vuosi) written as vuonna?

When saying that something happens 'in a year' or 'last/next year', Finnish uses the essive case ending -na/-nä to express points in time. The word vuosi has an irregular essive form, which becomes vuonna.