Sreening Genomic or cDNA libraries

I've purified a protein and I'm interested in identifying splicing patterns and promotor elements that contribute to expression of the RNA.

The following is the answer to this question, which I don't understand at all. Can someone better explain this?

Obtain protein sequence, make degenerate oligonucleotide, use oligo to screen a genomic library, obtain a clone with DNA that would encode protein (check by sequencing the DNA). Sequence will give you info about promoter and possible splicing patterns of the RNA. Could use the DNA to probe for RNA sequences (northern blot), or to screen a cDNA library (sequence appropriate clones which would represent the RNA sequences).