6 Then I saw another angel flying in midheaven, with an eternal gospel to proclaim to those who live on the earth—to every nation and tribe and language and people. 7 He said in a loud voice, “Fear God and give him glory, for the hour of his judgment has come; and worship him who made heaven and earth, the sea and the springs of water.”
I tried to get a better understanding of the term "midheaven"; apparently this is an old astronomical/astrological term that means, according to wiktionary, "the intersection of the ecliptic and the meridian." This really didn't help me much. As astrology and astronomy were combined historically far more so than they are now, it is a term that probably would have been more familiar to people at the time of this writing than it is to us. Biblehub.org has a bit more information here.
The writer at gotquestions.org says verse 6 of this chapter is the only reference to "the eternal Gospel" in the entire Bible. The writer says, "The gospel is 'everlasting' in that is an eternally unchanging message. False doctrines come and go, and new teachings are like wind and waves that toss the unsuspecting every which way."The Gospel itself is the message of redemption through Christ due to his sacrifice for humanity on the cross. These verses imply that though we have been assailed throughout human history with many false gospels, the reality of Salvation through Christ is the one that is true and eternal. I really hope everyone will accept the Salvation the Christ offers us so that we can all meet God and Christ in Heaven and be saved from the fate of the beasts from the earth and sea and all who follow them.
A Prayer for Salvation from Christ:
Lord
Jesus, I confess my sins and ask for your forgiveness. Please come into
my heart as my Lord and Savior. Take complete control of my life and
help me to walk in Your footsteps daily by the power of the Holy Spirit.
Thank you Lord for saving me and for answering my prayer.
A more detailed step by step process:
https://www.wikihow.com/Accept-Jesus-Into-Your-Life