This is just off the top of my head, so you may get a better answer, but this is what I recall. Transcendance refers to what lies outside yourself, immanence to what lies within.
God is wholly transcendant, because His creation lies wholly outside of him, yet he governs it through his providence.
At the same time God is immanent in his creation, because his creative power lies at the center of every created thing's existence. God creates everything from nothing. The corollary is that if he walks off and leaves his creation, it is held in existence by the material from which it was created--i.e., nothing. That fact that everything continues to exist means that God must be immanent in creation.
Not only that, but for human beings God is immanent within our very being, not only through his creative power (as he is in all of creation) but through Grace, by which he pitches his tent within our soul, to use the phraseology of the prologue of the gospel of John.