Captain America’s first appearance was in Captain America Comments #1 in 1941, but after the 1940’s and a short failed revival in the 50’s he remained dormant until he was brought back in Avengers #4 . After which he became a steady member, and even leading force for the marvel group. In that fateful issue, he was recovered by the avengers, having thawed out of an icecap. His first mission ‘with the avengers revolves around him saving them from a suspended state, and then helping an alien return home; all while Namor seeks to stop the heroic team.
After which, he quickly works with the team to track down the Hulk, Face off the lava Men and much more.
Reading Order & Appearance list for Captain America*:
*Based of of what I have reviewed so far in silver aged comics.: