Four Ways –
1) Test flight : http://help.testflightapp.com/
2) Install from iTunes – Create .ipa as ad-hoc and normal sync with ipad & itunes.
3) Or best way you can create a URL for install while creating ipa select as enterprise and create index file with plist. This will work with individual developer account too.
4) Diawi : http://www.diawi.com/
Tested all above step.