well the basic explanation would be:
- have
amxx running on your server
- download the source code to whatever plugins you want from the downloads section
- compile the source code either locally or with an online compiler (found at
dodplugins.net under 'help tabs' on the nav menu, or theres also one on the
amxx website)
- put the compiled plugin (*.amxx file) into the ../addons/amxmodx/plugins/ directory on the server
- add a line with the full file name (for example: dod_smokegrenade2.amxx) into the plugins.ini file located in ../addons/amxmodx/configs/
- change the map or restart the server