3. deild karla is a football league in Iceland. It is the fourth level, and second-lowest division, in the Icelandic football league system.
How to enable the Icelandic lower leagues in FM171 - Download the file.
2 - Move the file across to your Editor Data folder located in Documents > Sports Interactive > Football Manager 2017 > Editor Data
3 - Load Football Manager and start a new career.
4 - Click Database in the top-right of the screen, and make sure this database is ticked.