Please read chapter 5 in “An Introduction to Statistical Learning”, which looks at bootstrapping and cross-validation. In addition will we also talk about data leakage some more. We will also be talking about evaluating model performance so please also read chapter 9 - Judging model effectiveness in "Tidy Modeling with R, which we will use as the introduction for the R package yardstick.
The accompanied tidymodels labs can be found here.