Josef Hansen b. 11 Apr 1890 Christiana

I am new to this forum, and new to research on my Norwegian ancestors. I am looking for Josef Hansen, born 11 Apr 1890 in Christiana and his future wife, Marie Christensen born on an unknown date in 1888. According to the family he is from Christiana, but on his draft record he indicated he was from Oslo. On their marriage certificate in Illinois it states that Josef's parents are Charles Hansen and Mashel Andersen - I believe the "Mashel" is a phonetic spelling of "Michelle" so it could be her name was Mikaela. Marie Christensen's parents are noted as Otto Christensen and Karen Petersen. Can anyone give me some guidance in how to go about searching for these two people? In reading about the naming conventions in Norway, I'm not even sure where to start. Thank you for any help you can give me, I do appreciate it! Nancy