Transcription is a process by which RNA is obtained from a strand of template DNA.
For this to happen, the DNA strand must first be opened allowing the RNA polymerase to dock and start binding nucleotides depending on the DNA sequence. Once the RNA is finished synthesizing, it will exit into the cytoplasm and the RNA polymerase will uncouple from the DNA allowing it to close again.
Therefore, the order would be as follows:
DNA unzips
RNA polymerase adds nucleotides
RNA is fully synthetized
DNA reattaches together