What did the Lord say to His parents when He was but twelve years of age - "Wist ye not, that I must be about my Father's business?" Luke 2:49.
And what did He assert to the Father, that day in Gethsemane?
"O my Father, if it be possible, let this cup pass from me: nevertheless not as I will, but as thou wilt." Matthew 26:39.
In both cases, He demonstrated that a life of service unto God is not a passive one, rather, it is one of the individual's active participation with God in those "good works, which God hath before ordained that we should walk in...." Ephesians 2:10.
That is how the fruit of the Spirit comes about.
As the Believer keeps his or her nose in The Book, learning from it what those good works are that God had before ordained that he or she should walk in, and then by faith walks in said good works, the Spirit's intended fruit through said walk by faith in said good works, is manifested through them.
This is also evident in Paul's reminding the Galatians that if they will "Walk in the Spirit," they "shall not fulfil the lust of the flesh." Galatians 5:16.
To walk in the Spirit, then, is to deliberately choose to walk by faith in an understanding of your stand before God in Christ, as revealed to you by God through His Spirit in His Word (that He through His Spirit, inspired its writers, to write), as a result of your time in His Word.
Or, put another way...
Colossians 3:16 Let the word of Christ dwell in you richly in all wisdom; teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord.
Galatians 5:16 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
2 Timothy 2:15.
It sounds like you don't believe someone might automatically know what the things of the Spirit are that he should do. The Bible helps. Other believers help. A relationship with God and Jesus helps.