Anyone intending to use controlled substances for research or teaching must be registered with the DEA, using DEA Form 225. There is an on-line registration option and a paper registration option. (The paper registration option MUST be used if you are applying to use Schedule I drugs, but may optionally be used for other drugs.)
Instructions can be found at http://www.deadiversion.usdoj.gov/drugreg/reg_apps/225/225_instruct.htm. Be sure to note the following (bullets 3 and 4 may appear to diverge from the instructions but are essential):
Researchers must renew their DEA registrations annually. The renewal process is described at https://www.deadiversion.usdoj.gov/webforms/jsp/regapps/common/renewalAppLogin.jsp. Be sure to follow the instructions above regarding checking the "exempt" box.
A copy of the annual or renewal registration should be sent to:
Office of Research Integrity
3100 Marine Street, ARC Rm A15
Boulder, CO 80309