CRPF (Central Reserve Police Force) is the biggest of India's Central Armed Police Forces. It functions under the guidance of Ministry of Home Affairs of the Govt. of India. It was formed on 27th July, 1939.
It works under following conditions:
Paramilitary law enforcement, counter insurgency, armed response to civil unrest, counter terrorism, special weapons operations.
Counter terrorism, special weapons and tactics, protection of VIPs.
Protection of international or domestic VIPs, protection of significant state asseets
As on 12th Dec, 2015, there is no recruitment notification released for the post of ASI by CRPF.

So you have to wait till the next notification released by CRPF to apply for it.
However you can check for the notification on CRPF website by following ways
Firstly, go to CRPF website, the page looks like



Then place cursor on “Recruitment” and click on “Recruitment”, the new page open look like



Here you will find details about the recruitment notifications.

Contact Information:
Directorate General
Central Reserve Police Force
Block No.-1, C.G.O. Complex
Lodhi Road
New Delhi-110 003, India