The file README.txt from sage-6.1-x86_64-Darwin-OSX_10.9_x86_64-app.dmg, for Mavericks (OS X 10.9.1)says that:
3) Use finder to visit the sage folder you just copied it and double click on the "sage" icon.
4) Select to run it with "Terminal": Choose Applications, then select "All Applications" in the "Enable:" drop down. Change the "Applications" drop down to "Utilities". On the left, scroll and select "Terminal". Click "Open", then in the next dialog select "Update".
5) Sage should pop up in a window.
Can someone explain the step 4? For example, I am unable to find "Enable:" drop down.