You could search before posting, there are tons of examples in these forums.
PHP Code:
#include <amxmodx>
#include <amxmisc>
new AUTHOR[]="T-z3P"
new VERSION[]="0.1"
new PLUGIN[]=""
public plugin_init()
{
register_plugin(PLUGIN,VERSION,AUTHOR)
register_clcmd("say /admin","cmdAdmin")
register_clcmd("say_team /admin","cmdAdmin")
}
public cmdAdmin(id)
{
show_motd(id,"addons\amxmodx\configs\admin.html","Admin")
return PLUGIN_HANDLED
}
Compile this and make a html file called "admin.html", add your information in it and then place it in "cstrike/addons/amxmodx/configs".