Trying the Handson challenge for Admin Beginner>Data Management>Data Import. When Import the csv file, some fields are unmapped and when I try to map them to Salesforce fields, I get an error message 'You need to map the required field Contact: Last Name'

Again @Karthick G, you should start a new question, this one is too old. Hard to tell without having a screenshot of the error, but please start a new thread, this question is too old. If you start a new question, more people would see it, hence you have a better chance of getting an answer