Hi amar,
Check the below example.
HTML
<script type="text/javascript" src="//tinymce.cachefly.net/4.0/tinymce.min.js"></script>
<script type="text/javascript">
tinymce.init({
selector: 'textarea',
width: 200,
height: 200,
resize: false
});
</script>
<textarea name="txtRichTextBox" rows="2" cols="20" id="txtRichTextBox"></textarea>
Demo