How were eastern europeans affected by communism after ww2?

Simply put, by coercion.

There was a very simple process that followed:

(1) the Red Army invades the countries, on the pretext of "liberating" them - this gives a plausible veneer to a treacherous end;

(2) whilst occupying, Soviet commissars would prop up the local communist party (typically, enjoying only minimal support from the country's population, unless also nationalist) - this is so as to have a puppet regime-in-waiting;

(3) under Soviet occupation, typically some sort of a "referendum" or "plebiscite" will be held, at which SUDDENLY the voters will "decide" to abolish the previous constitution and to enact one that practically gives sole powers to the local communists - this is to give the effective coup d'etat a veneer of legitimacy;

(4) once installed in power, the communist party will effectively take over the machinery of state by staffing all key posts with its members;

(5) through the use of secret police and kangaroo courts, opposition, incl. those of the original governing class who did not have the good sense to escape, will be physically eliminated, sentenced to long prison terms, exiled, otherwise incarcerated;

(6) a the takeover of the state is usually followed by a takeover, through nationalisation or outright confiscation, of the economy, giving the regime financial muscle;

(7) the established position will be upheld by the same means it was acquired and with unparalleled degree of ruthlessness, with the country taken over being treated as a wholly-owned subsidiary of Kremlin Holdings.