And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death

"And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night." - Revelation 12:10  

"And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death." - Revelation 12:11  

“And they overcame him by the blood of the Lamb” – the death, burial, and resurrection of Jesus 

“And by the word of their testimony” – they repented of their sins, were baptized in Jesus name for the remission of their sins, and received the gift of the Holy Ghost. 

"The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world." - John 1:29  

"And this gospel of the kingdom shall be preached in all the world for a witness [testimony] unto all nations; and then shall the end come." - Matthew 24:14  

The gospel preached is Christ died for our sins, was buried, and rose again: 

"Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; by which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; and that he was buried, and that he rose again the third day according to the scriptures:" - 1 Corinthians 15:1-4  

We obey the gospel of Jesus by becoming dead to sin, buried with Jesus by baptism, and raised to Life by the infilling of His Spirit (the glory of the Father). 

"God forbid. How shall we, that are dead to sin, live any longer therein?  Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life." - Romans 6:2-4  

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call." - Acts 2:38-39  

"And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: and that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. And ye are witnesses of these things. And, behold, I send the promise of my Father upon you: but tarry ye in the city of Jerusalem, until ye be endued with power from on high." - Luke 24:46-49  

"But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth." - Acts 1:8  

“And they loved not their lives unto the death.” – 

"And ye shall be hated of all men for my name's sake: but he that endureth to the end shall be saved." - Matthew 10:22  

"And because iniquity shall abound, the love of many shall wax cold. But he that shall endure unto the end, the same shall be saved." - Matthew 24:12-13  

"For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;" - Hebrews 3:14 KJV ["For we have become partners with Christ, if in fact we hold our initial confidence firm until the end." - Hebrews 3:14 NET] 

"Fear none of those things which thou shalt suffer: behold, the devil shall cast some of you into prison, that ye may be tried; and ye shall have tribulation ten days: be thou faithful unto death, and I will give thee a crown of life." - Revelation 2:10