First of all you will need to download the zip file from your ThemeForest account. For that, you can go to https://themeforest.net/downloads and click the download button next to the Drift item.
Once the zip file is successfully downloaded, you will need to extract that. Extracting the zip file will create a folder with following sub-folders:
In this step, you can copy the classic-version/ folder and paste that to the location you want to setup your project at.
Once the folder is copied successfully, you can rename this folder with the name of your project. For example, we are naming this as my-first-drift/
Apart from above, rest folders are different-different layout folders and you can remove all of those except the one you want to use in your project. For example, if you want to use the default layout, then keep the default/ folder and remove the rest.
There is one more thing to do yet before we say cheers!
In the assets/css/ folder, there are also various layout related folders.
You can also remove these unnecessary folders just like you did in above steps.