You can't import 2018 stats because they aren't in the database. You'd have to use 2017 stats.
Assuming you are using Windows you create a new text file. Use a file name that is descriptive so you know what it's for. ex) 2017 rockies import.txt sample line for Trevor Story.
storytr01, 2017, col
playerID from baseballref, year, team to import to (if blank will import to free agents)
The team to import to is the team's abbreviation from your league setup screen.
The manual describes how to import using the text file.
http://manuals.ootpdevelopments.com/...torical_wizard