Hi yogita,
data layer example :
<script type="text/javascript">
window.dataLayer= {
'pagename':"indexPage",
'City' : "Mumbai"
}
</script>
Since you are using data Layer here you can do it like this.
Go to the data element create new -> type JS object -> path you can set like
dataLayer.City
This will access the value in global parameters.
Regards,
Ketan Pardeshi