Hi R1TechGaming here, i will tell you how to transfer the file to saved game file

step 1: Open file explorer
Step 2:Open Documents
Step 3:Open Universe Sandbox
Step 4:Open Simulations Folder
Step 5:Pate the files named [MoStar Solar System.ubox]
Step 6:Open Universe Sandbox and click the open button in the menu and click the my simulations button and there you have it, click the simulation and have fun:)