If you need to authorize someone as a representative, here is a sample template you can use to write an authorization letter for a representative.
To Whomsoever It May Concern,
This letter is to inform you [I/we] the undersigned, authorize the [Designation], [Mr./Ms. Name], to represent [me/us]. I appoint [him/her] her to take complete responsibility and act on [my/our] behalf for the [event]. In [my/our] absence, [he/she] shall have the authority equivalent to [mine/ours] and unhindered decision making capacity.
This authorization also extends in matters of the signing of documents and making independent choices. The applicant will provide you with [his/her] identity proof for verification of authenticity as well. Your cooperation is requested for the same. Kindly take note and contact me at [Phone No.] in case of further queries.