If all images are in one folder you can make a variable like path_to_dataset = “your_path” Split normally and then just add dataset path to image name

You might shuffle dataframe (df.sample(frac=1)) and then just take first 80 % of samples as train and other 20 as test

Also you might use sklearn train_test_split

I started with this course https://mlcourse.ai/book/index.html, as for me it has nice, more mathematical explanations how models like linear regression, logistic regression, decision trees work under hood, and also it has some other topics covered