WT "Salvation" = Jehovah deeming you worthy of a resurrection (or surviving Armageddon)
How obtained = "exercising faith" in Jehovah's name and in Jesus' ransom sacrifice = serving Jehovah as part of his earthly organization (the Watchtower Society) by obeying "the faithful and discreet slave" (the GB) sufficiently well and remaining faithful to the end of your life.
"Sufficiently well" = only Jehovah knows (most likely more than what you have been doing)