Thoughts on Westminster Confession of Faith, article I.6, which you can find here.
The revelation of God in Scripture is complete. It doesn’t give specifics on everything, but the principles given apply to everything. There is no inspired technical manual on aircraft mechanics, but there is instruction on how to work in any calling or career (Colossians 3:17, 22-25).
Some things are not explicitly taught in Scripture, but can be inferred from it. An example might be that wives and citizens ought not submit to their husbands and magistrates when asked to oppose God. We see this in story form in Abigail going behind Nabal’s back, and the apostles telling the temple leadership they must obey God rather than men. But the principles aren’t laid out in instructive form. We often need to infer from events in the Bible whether this is model behavior or not, using the clearer parts of Scripture to do so.
We must be careful not to add to Scripture. Some cults do this literally, but many Christians do it functionally by giving their favorite teachers more weight than the Bible, or chasing the leading of the Spirit more than heeding Scripture. Jesus corrected the Pharisees for “teaching as doctrines the commandments of men” (Matthew 15:9). We need the Spirit’s illumination to read and understand and profit from Scripture, but we do not need or expect new revelation from the Spirit beyond Scripture. Illumination by the Spirit is not same as inspiration.
Although the Bible addresses everything in principle, it does leave us to the wisdom we find in creation when we get down to the details on many things. There is no detailed schematic for how big a church should be, what kind of building to have, how long a worship service should last, how the leadership should be structured. This in no way threatens the idea of the sufficiency of Scripture. The Bible gives us “all things that pertain to life and godliness” (2 Peter 1:3).