EAP245 is an AP but can't work as an Extender.
You may leave it as a Standalone mode (If you have a relatively small-sized wireless network and only one or just a small numberof EAPs need to be managed, you can directly use the web browser to manage each EAPon its own management web page. In such case, the EAP works in Standalone mode (FATmode), which means that it works independently as a standalone access point).

For more details, please check it' s User Guide: http://static.tp-link.com/2017/201712/20171201/1910012254_EAP_UG.pdf