Hi,

Please put this code on Appointment entity on load.

function setAppointmentDetails(){
if(Xrm.Page.ui.getFormType() == 1){
var regardingObject = Xrm.Page.getAttribute("regardingobjectid");

if (regardingObject && regardingObject.getValue() && regardingObject.getValue()[0].entityType == "account")
{
var regardingObjectId = regardingObject.getValue()[0].id;
regardingObjectId = regardingObjectId.slice(1, -1);
var req = new XMLHttpRequest();
req.open("GET", Xrm.Page.context.getClientUrl() + "/api/data/v8.2/accounts("+regardingObjectId+")?$select=address1_city,address1_country,address1_line1,address1_line2,address1_line3,address1_postalcode,address1_stateorprovince,name", true);
req.setRequestHeader("OData-MaxVersion", "4.0");
req.setRequestHeader("OData-Version", "4.0");
req.setRequestHeader("Accept", "application/json");
req.setRequestHeader("Content-Type", "application/json; charset=utf-8");
req.setRequestHeader("Prefer", "odata.include-annotations=\"*\"");
req.onreadystatechange = function() {
    if (this.readyState === 4) {
        req.onreadystatechange = null;
        if (this.status === 200) {
            var result = JSON.parse(this.response);

            var address1_city = result["address1_city"];
            var address1_country = result["address1_country"];
            var address1_line1 = result["address1_line1"];
            var address1_line2 = result["address1_line2"];
            var address1_line3 = result["address1_line3"];
            var address1_postalcode = result["address1_postalcode"];
            var address1_stateorprovince = result["address1_stateorprovince"];
            var name = result["name"];

			if(name)
			{
			var subject = "visit "+ name;
			Xrm.Page.getAttribute("subject").setValue(subject);
			}

			var address = "";
			if(address1_line1)
			{
			var address = address + address1_line1;
			}
			if(address1_line2)
			{
			var address = address + " " + address1_line2;
			}
			if(address1_line3)
			{
			var address = address + " " + address1_line3;
			}
			if(address1_city)
			{
			var address = address + " " + address1_city;
			}
			if(address1_stateorprovince)
			{
			var address = address + " " +  address1_stateorprovince;
			}
			if(address1_postalcode)
			{
			var address = address + " " +  address1_postalcode;
			}
			if(address1_country)
			{
			var address = address + " " +  address1_country;
			}
			Xrm.Page.getAttribute("location").setValue(address);


        } else {
            Xrm.Utility.alertDialog(this.statusText);
        }
    }
};
req.send();
}
}
}