You will have to contact the inmate's counselor or case manager to find out what the procedure is for the signing of legal documents. It's not a hard process, as this is normal for these facilities.
https://www.inmateaid.com/ask-the-inmate/my-husband-got-locked-down-last-night-for-what-idk-but-i-need-to-have-him-sign-a-power-of-attorney-paper-will-he-be-able-to-do-so#answer
Accepted Answer Date Created: February 11,2021