The Nazis were very effective at taking control of Germany and removing opposition. They used legal methods (the March 1933 election, the Enabling Act), party organisation (propaganda got the votes in, party contacts got huge donations from business) and illegal methods (intimidation and violence).
The Reichstag fire
On 27 february 1933, the Reichstag building was burned down. A Dutch communist, Marinus van der Lubbe, confessed. Thousands of communists were arrested on 8 February. Hitler persuaded Hindenburg to declare a state of emergency and call an election.
The Nazis won 288 seats, and made deals to get the two-thirds majority needed to change the constitution.
The Enabling Act in March 1933 gave Hitler the power to make whatever laws he wanted without Reichstag approval for four years.