When Jesus says “Abide in Me” in John 15 we learn what it means to abide in Him in John’s 1st epistle, 1 John chapter 2. “If that which you heard from the beginning abides in you, you will also abide in the Father and in the Son. And this is what He promised us, even Eternal Life.
"Let that therefore abide in you, which ye have heard from the beginning. If that which ye have heard from the beginning shall remain in you, ye also shall continue in the Son, and in the Father. And this is the promise that he hath promised us, even eternal life." 1 John 2:24-25
The way to abide is to hold fast to the doctrine of Christ, the Gospel, His Testimony, and not be moved away from it. Paul encourages the same thing, to “continue in the faith, grounded and steadfast and not being moved away from the hope of the Gospel which was proclaimed to you”.
"If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister." Col 1:23
The Gospel does the work of discipleship for us. Jesus said in John, “If you continue in my word, you’ll be my disciples indeed, and you will know the truth, and the truth will make you free”
"Then said Jesus to those Jews which believed on him, If ye continue in my word, then are ye my disciples indeed." John 8:31
Read the book Here Christ As Righteousness Sanctification and Reward