so "cd" to whichever directory macshift is in. so if it's in C:\, type "cd C:\". Also make sure that you are running as admin.
So:
open command prompt as admin.
type: cd C:\
type: netsh wlan set hostednetwork mode=allow ssid=attwifi key=password
type: netsh wlan start hostednetwork
goto network and connections, right click your ethernet connection and select properties. in the sharing tab, tick both boxes and share with "Local area connection xx"
type (back in command prompt: macshift -i "Wi-Fi" 4E53504F4F46
and on your 3DS, delete all other access points and then manual setup>search for points. Select attwifi, the password is "password"
and then see if you get a hit. If you do, then you can download my cycler so you can cycle through new MACs and get up to 100 hits.
It still doesn't seem to work somehow(the network works, but I still don't get any streetpasses), is there a way to reset all the stuff I've done so I have a clean start? I think I screwed up somewhere.