Select element by path and change innerHTML
<script>
var select=document.querySelector("#footer .footer-newsletter p");
select.id = "nladdon";
document.getElementById("nladdon").innerHTML = "My First JavaScript";
</script>
<script>
var select=document.querySelector("#footer .footer-newsletter p");
select.id = "nladdon";
document.getElementById("nladdon").innerHTML = "My First JavaScript";
</script>