@Funkywalt You need to download the loops. They are probably inside a ZIP file. You can extract the ZIP file by right clicking on it. Extract the loops in a folder of your choice. Inside Music Maker go to the internal file browser tab and navigate to the folder with your loops and drag and drop them into your project. Alternatively you can drag and drop the loops from the Windows Explorer into your project.

I don't think you can add the loops to the Loops manager tab in Music Maker. Only Magix Soundpool loops can be added to this tab and BIGCITI loops are very likely not organised like Soundpools and therefore cannot be displayed in the Loops tab. But it should work fine with the file browser.