How do I go about marriage by proxy
I'm active duty military my fiancé civilian state of Florida

Doesn't look like you can do it in Florida.

http://www.weddingvendors.com/marriage-license-laws/united-states/florida/f

Are proxy marriages legal? No, marriage by proxy is not allowed.

Proxy Marriage -- Where You Can Have a Proxy Wedding (http://marriage.about.com/cs/legalities/a/proxymarriage.htm)

Where You Can Get Married By Proxy:
Four states in the United States allow proxy marriages:

Calfornia Colorado Texas Montana.

Most of the proxy marriage laws are limited to members of the armed forces who are deployed for conflicts or wars. Some have residency requirements.

A double-proxy marriage is a marriage where neither party is present. In the United States, the only state to allow a double-proxy marriage is Montana, though not all Montana counties will allow the proxy marriages.