File > Save As...
Rename your file (eg. Final 1 illustration). Choose where you want to save it (whether it is your desktop or on your usb or harddrive) and make sure the format is Adobe Illustrator (ai).
To put it on your blog (and for submitting your work at the end of the semester) it will need to be a JPEG file.
File > Export
File format will be JPEG.
For printing the color model will be CMYK, quality will be 10 Maximum and the resolution will be High (300ppi).
For your blog, the colour model will be RGB, quality can be your choice (medium is fine) and the resolution will be 72ppi)