There are two common ways to make this firmware "work" on your access point:

: Many used Cisco 3700s are sold as AIR-CAP (Lightweight) models; this file is the "magic key" needed to convert them to Autonomous . Installation Guide

The file name identifies its specific purpose within the Cisco ecosystem:

is the specific Cisco IOS firmware file used to run Cisco Aironet 3700 series access points in Autonomous mode . This version allows these access points to function as independent, standalone units without requiring a Cisco Wireless LAN Controller (WLC). Overview of the Firmware

AP 3702i - IOS version for Autonomous Mode - Cisco Community

: Refers to the internal hardware generation, specifically for the Aironet 1700, 2700, and 3700 series.