Cisco has really made configuring a WLAN controller and the associated access points simple. Today I configured a Cisco 2504 WLAN controller and 6 1242AG’s with 2 SSID’s in less than 2 hours. That is including the time it took to un-pack everything. I love it when a product works and makes my job easier.
Cisco makes it very simple to convert an autonomous AP to lightweight mode.
Step 1- Ensure the autonomous AP is running version 12.3(7)JA or later. If not upgrade to this version.
Step 2- Download the upgrade tool and upgrade image by going to http://www.cisco.com/cisco/software/navigator.html, and selecting your product.
Step 3- Install the tool on your computer.
Step 4- Fill in the information for your AP, file location, and controller and then press the start button.
For more detailed information http://www.cisco.com/en/US/docs/wireless/access_point/conversion/lwapp/upgrade/guide/lwapnote.html