Save A Project
Save your work often.  You never know when the power might go off. :)

Choose Save or Save As...  from the File menu, navigate to a save folder, type in a name and click OK.

Your Mixcraft project will be saved as a Mixcraft project file (MX4).  You can also save it as a Project Template (MX4Template).

Alternatively, you can save the project by clicking the Save button on the toolbar.  

If you want to save your project as a single MP3, WAV, OGG or WMA file, you should mix down your project to an audio file.