How to enable apache module

i am using Prestashop on Webmin, but i need speed up my website. I have add some code to .htacces (mod_expires) but it not working. May be this module disable, can you help me to enable apache module for webmi. I am beginer and using windows, so i dont know to to enable this module. Hope you can help. Some information of my sever

Operating system Debian Linux 6.0 Webmin version 1.740 Kernel and CPU Linux 2.6.32.46-xenU on i686 Processor information Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz, 2 cores