In the webassist/plugins/google_map/google_javascript/wagmp_map_1.php file, find the following code:
var address_0 = {
street: '<?php echo str_replace("'", "\'", "".$WAGLOBAL_Address .""); ?>',
city: '<?php echo str_replace("'", "\'", "".$WAGLOBAL_City .""); ?>',
state: '<?php echo str_replace("'", "\'", "".$WAGLOBAL_State .""); ?>',
zip: '<?php echo str_replace("'", "\'", "".$WAGLOBAL_Zip .""); ?>',
country: '<?php echo str_replace("'", "\'", "".$WAGLOBAL_Country .""); ?>',
infowindow: 'default',
infowindowtext: '<span style="font: 12px Verdana, Arial, Helvetica, sans-serif; color: black;"><?php echo str_replace("'", "\'", "<strong>Address:</strong><br />".$WAGLOBAL_Address ."<br />".$WAGLOBAL_City .", ".$WAGLOBAL_State ." ".$WAGLOBAL_Zip ." ".$WAGLOBAL_Country .""); ?><br /><a href="javascript:updateInfoWindow()">get driving directions</a></span>',
full: '<?php echo str_replace("'", "\'", "".$WAGLOBAL_Address .""); ?>, <?php echo str_replace("'", "\'", "".$WAGLOBAL_City .""); ?>, <?php echo str_replace("'", "\'", "".$WAGLOBAL_State .""); ?>, <?php echo str_replace("'", "\'", "".$WAGLOBAL_Zip .""); ?>, <?php echo str_replace("'", "\'", "".$WAGLOBAL_Country .""); ?>',
isdefault: true,
addressType: 'address',
loop: '',
latitude: '',
longitude: '',
markerStyle: 'House',
markerColor: 'Slate'
};
in that block change:
addressType: 'address',
loop: '',
latitude: '',
longitude: '',
to:
addressType: 'coordinates',
loop: '',
latitude: '<your latitude>',
longitude: '<your longitude>',
where <your latitude> and <your longitude> are the coordinates you would like to use.