Since 5.3 you have to download one module each target platform.

http://answers.unity3d.com/questions/1114042/no-mac-build-option-on-pc.html

1: Log in.

word press login

2: Create a new completed project

complete1

 

3: Describe your project

complete2

4: Insert a gallery using your own photos and photos from your project photoshoot. Be sure to insert GALLERY as it looks nicer.

complete3

Click “Add Media”.

complete4

Be sure to choose “Create Gallery” and click “Upload Files” to upload your images.

complete5

Once your images are uploaded, you will see a screen like this. The images you uploaded should already be selected for you. Click “Create a new gallery” at the bottom right.

complete6

Finally, press “Insert Gallery” at the bottom right.

5: Upload your instruction manual and thumbnail for your project

c1

DO NOT UPLOAD ANYTHING TO GAME PHOTO. IT’S BROKEN. USE THE GALLERY METHOD OUTLINED IN THE PREVIOUS STEP.

7: IMPORTANT!!! Set the category to the project assignment you want to submit to.

c2

 

6: HIT PUBLISH!  

Otherwise we won’t be able to see your project!

hit publish