Download the zip file containing the saves provided here and extract it. In the folder you extracted, you will also find more folders for every level each containing a "user_data.sol" file.

In your computer, go to "C:\Users<WindowsUserID>\AppData\Roaming\Macromedia\Flash Player#SharedObjects". (here <WindowsUserID> is the name of the profile you use to login to Windows) The "AppData" folder may not be visible, but you can type it out in the address bar to reveal it.

After going into the "#SharedObjects" folder, you will probably find a folder with a bunch of random alphabets and numbers.

Inside that you will find names of websites you played flash games on. You will have to find the .sol file corresponding to Raft Wars 2. It will most likely be named "user_data.sol".

Replace this file with the "user_data.sol" file corresponding to the level you want to practice from the folder you extracted in Step 1.