Any ordained minister can hear confessions, bearing in mind that confessions are to be held absolutely and unconditionally confidential. Very few are able to perform this duty adequately, and taking on this responsibility should not be entered into lightly. If you are fully confident of your ability in this regard, then it is highly probable you are wrong.
Make your self fully aware of your legal status with respect to confidentiality. Some jurisdictions do not recognize your right to maintain full confidentiality, others make exceptions, particularly for planned acts which affect the safety of others, and with respect to crimes against children.
If you choose to take on the hearing of Confessions, remember that as an Agnostic minister you have no power to forgive on behalf of a purported supreme being, nor can you forgive on behalf of the rest of humanity, Your only power is to listen sympathetically, and then try to assist the person in coming to terms with his or her guilt.
This may involve (not an all-encompassing list):
It should not involve multiple rote repetitions of meaningless formulaic phrases, nor should it give the person a "free pass" on past or future crimes.