How does an inmate file for an electric monitor?

Surely, you jest. You need to give us some facts. Attorneys deal with facts and the law. Without facts we cannot apply the law.

By asking his attorney to do so for him. That is how.

I have never heard of an inmate "filing" for an electronic monitor. It probably depends on the jurisdiction (location) as well. Each jail and each court do things a little differently. In most instances, the judge would be the one to determine whether or not you are to do custody time or are released on "EM." Sometimes, though, the sheriff or whomever is in charge of the jail, can make a decision to release a person on EM under the re-alignment laws. In the first instance you would need to get the judge to modify the sentence; in the second you would have to check with the sheriff to see what the process is and whether or not you qualify, or can apply for EM.

You need to address bond to the judge and ask/argue that he should be bonded out and, as a bond condition, he be placed on electronic tether. There is a charge for the tether service.