Is the Selma Marches connected to the Civil Rights movement and how they were able to gain the right to vote ?

Yes

In March 1965, thousands of people held a series of marches in the U.S. state of Alabama in an effort to get that right back. Their march from Selma to Montgomery, the capital, was a success, leading to the passage of the Voting Rights Act of 1965. ... They said it did not always guarantee the right to vote.

after the roman empire, the catholic church began to unify by taking on many duties of a government.

congress also has implied powers, which derive from the necessary and proper clause of the constitution and permit congress "to make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states.