Each time you start the AChat client, it will check automatically if any upgrade is available. These upgrades may contain new objects (e.g. clothing), new program features, or function corrections.
The available upgrades will be installed automatically, you have nothing to do except waiting a few seconds (or minutes, if it is a major upgrade).
This way your client will be up to date and error free, and will contain the latest functions and objects without any additional effort on your side.