Background: Walter Marty "Wally" Schirra Jr. (March 12, 1923 - May 3, 2007), (CAPT, USN), was an American naval aviator and astronaut. He was one of the original seven astronauts chosen for Project Mercury, the first effort by the United States to put humans in space. On October 3, 1962, he flew a six-orbit, nine-hour, Mercury-Atlas 8 mission becoming the fifth American, and ninth human, to travel to space. In the two-man Gemini program, he achieved the first space rendezvous, station-keeping his Gemini 6A spacecraft within 1 foot (30 cm) of the sister Gemini 7 spacecraft in December 1965.
Context: In mid-1966, Schirra was assigned to command a three-man Apollo crew with Donn F. Eisele and R. Walter Cunningham to make the second manned flight test of the Apollo Command/Service Module, with a mission profile identical to Apollo 1. Schirra argued against a repeat mission, and his crew became the backup crew for Gus Grissom, Ed White and Roger Chaffee. Schirra's crew conducted tests in the command module on January 26, 1967, and were enroute to Houston the next day when Grissom, White, and Young were killed in a fire during a test. Schirra's crew became the prime crew of the first manned flight. This became Apollo 7 in the program's revised mission numbering plan, and was delayed to the fall of 1968 while safety improvements were made to the Command Module.  Schirra gained a sense of security from having Guenter Wendt, a McDonnell Aircraft employee, as the pad leader responsible for the spacecraft's launch readiness. But since the Apollo contractor was North American Aviation, Wendt was no longer pad leader. After the Apollo 1 accident, Schirra felt so strongly he wanted none other than Wendt as pad leader for his Apollo flight, that he pulled strings with his boss Deke Slayton and North American's launch operations manager Bastian "Buzz" Hello to hire Wendt as Apollo 7 pad leader. Wendt remained pad leader for the remainder of the Apollo and Skylab programs, and stayed on with NASA into the Space Shuttle program before retiring.  Apollo 7 was launched on October 11, 1968, making Schirra the first person to fly in space three times. Prior to launch, Schirra had objected because of high winds, which could have injured the astronauts in the event of an abort within the first minute of the mission. After reaching orbit, the Apollo 7 CSM performed space rendezvous and docking exercises with the S-4B stage to simulate retrieving the Lunar Module. On the second day of the mission, the crew conducted the first live television pictures publicly broadcast from inside a manned spacecraft.  During the mission, Schirra became sick with a head cold, which he passed to Eisele. Anticipating issues with congestion inside of a sealed spacesuit, Schirra proposed to Mission Control that they would not wear their helmets during reentry. Despite a request from Chris Kraft and Deke Slayton to wear helmets during reentry, Schirra, Eisele, and Cunningham refused and performed reentry without them. Apollo 7 landed southeast of Bermuda on October 22, 1968.  Prior to the Apollo 7 launch, Schirra had made the decision to retire after the flight, and left the NASA Astronaut Corps on July 1, 1969. Schirra's last assignment as an astronaut was to conduct the investigation into Neil Armstrong's Lunar Landing Research Vehicle crash.
Question: How did Schirra get involved with the Apollo program?. Whats the answer?
Schirra argued against a repeat mission, and his crew became the backup crew