To begin with, Hungarian stopped using passive voice a long time ago. People talked like that a hundred years ago, but not anymore. It was expressed with these suffixes: -atik, -etik. Examples:

it is said – mondatik
it is proclaimed – kihirdettetik

You can find such verbs in old texts. And what about the present time?

Hungarian expresses passive voice WITH ACTIVE SENTENCES!!!

So the formation goes like this:

3rd PP form of the verb with definite or indefinite conjugation

Examples:

The house was sold. – A házat eladták.
The soup is cooked. – A levest megfőzték.
The cars will be mended. – A kocsikat meg fogják javítani.

So Hungarian says they sold, they cooked, they will mend even if we don’t know who we’re talking about.

For a native English speaker the problem comes with Present Simple and Present Perfect if you want to translate English passive voice in Hungarian. Look at this:

to build = építeni > they built = építették
meg > verbal prefix expressing completeness

The house is built. – A házat megépítették.
The has been built. – A házat megépítették / építik.

Both sentences are translated with past tense in Hungarian. Why? Because the first Present Simple sentence says the house is built, so it is finished. And it had to be built in the past so that we can say it is built. Therefore Hungarian uses past tense.
As for the Present Perfect sentence, it can express the completeness or the continuity of an action, therefore Hungarian uses past tense for completeness and present tense for continuity.

The house has been built at last!
A házat végre megépítették!

The house has been built for a year now.
A házat már egy éve építik.

See what I mean? The first sentences refers to a house already finished, the second refers to a house still being built.

The rest of the tenses shouldn’t be a problem. You just use the same tense as in English. Examples:

Past Simple
The house was built.
A házat megépítették.

Future Simple
The house will be built.
A házat meg fogják építeni.

If it comes to a continous tense, you can put ÉPPEN before the verb, but it is not necessary. Hungarian verbs without a verbal prefix (like meg-) express continuity by themselves.

Present Simple Continuous
The house is being built.
A házat éppen építik.

Past Simple Continuous
The house was being built.
A házat éppen építették.

Future Simple Continuous
The house will be being built.
A házat éppen építeni fogják.

First digest the stuff above, and in the next entry I’ll write more examples and more stuff to learn about “passive voice”.