Firstly you will want to download Flash Games Archive

http://www.flashgamearchive.com/

Then you will need to download and unzip the game files also available in recourses.

https://drive.google.com/file/d/1Eo46L2dAT1pDha2aVtKFWXsbjCBRozyt/view

Boot up Flash Game Archive v3.exe or whatever version you have and find this button in the top right corner.

Click 'Choose SWF' and locate the unzipped game folder and open the .swf file.

It is possible to use save files to start just before any level. I have uploaded in resources saves from the start of each world/cavern and a 100% game file with all levels unlocked and the shop bought. The link is below.

https://drive.google.com/file/d/1hYCdM_b4x49J51qec30ixg0GDDHDAaEK/view?usp=sharing

To find saved data on windows, use windows + R to open the 'RUN' box and type %appdata%. Then go through 'Roaming', 'Macromedia', 'Flash Player', '#SharedObjects' and locate 'localhost'. There will be a 'Battle for Slugterra' folder with any saved data.

Let me know if there are any problems with the files. GLHF