The evaluation metric for this competition is AUC. The AUC is a commonly used evaluation metric for binary problems like this one. The interpretation is that given a random positive observation and negative observation, the AUC gives the proportion of the time you guess which is which correctly. It is less affected by sample balance than accuracy. A perfect model will score an AUC of 1, while random guessing will score an AUC of around of 0.5.

For every observation in the test set, submission files should contain two columns: UserID and Probability. The submission should be a csv file. The UserID should just be the corresponding UserID column from the dataset. The Probability column should be the predicted probability of the outcome 1 for that UserID.

As an example of how to generate a submission file in R, suppose that your test set probability predictions are called "testPred" and your test data set is called "test". Then you can generate a submission file called "submission.csv" by running the following two lines of code in R (if you copy and paste these lines of code into R, the quotes around submission.csv might not read properly - please delete and re-type the quotes if you get an error):
submission = data.frame(UserID = test$UserID, Probability = testPred)
write.csv(submission, “submission.csv”, row.names=FALSE)