In such sentences as in the example above, we usually use the past perfectThe aspect expressing completion. E.g.: He’s finished university. tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses. in the clauseA group of related words containing a subject and a verb. with hardly in it because it expresses an actionA general term expressing that somebody or something does something that happened before the action expressed by the other clause:

Hardly had I arrived home when the telephone rang. (= Soon after I arrived home, the phone rang.)

If we start the sentence with hardly, as in the example above, we use inversion (we invertA structure in which a verb or an auxiliary precedes the subject. E.g.: "Here comes the sun." the word order) and follow with had I arrived:

Hardly had I arrived home when the telephone rang.

Otherwise, we use normal word order and place the adverbA part of speech that modifies verbs, adjectives, adverbs and conjunctions. E.g.: I could hardly utter a word. ("hardly")ial hardly between the auxiliaryA helping verb used with main verbs to express mood, voice and tense. E.g.: I can't stand when I am disturbed. ("can", "am") had and the main verbA verb that can express an action or state in itself. E.g.: John likes squash a lot. ("like") arrived:

I had hardly arrived home when the telephone rang.

You can find more about inversion on these pages:

http://www.grammaring.com/partial-inversion
http://www.grammaring.com/hardly-scarcely-barely-no-sooner