<body>
<form method="post" action="xx.php" >
Enter Title of the Post<INPUT type="text" name="title">
<br/>
Enter Description
<textarea rows="10" cols="50" wrap="physical" name="post">
</textarea><br/>
<input type="Submit" value="Post">
<br/><br/>
<form enctype="multipart/form-data" action="xx.php" method="post">
<input type="hidden" name="MAX_FILE_SIZE" value="1000000" />
Choose a file to upload: <input name="uploaded_file" type="file" />
<input type="submit" value="Upload" />
</form>
How Do I get the user to write the text and browse the image, only after which pressing a single button would both upload the text and the file?
You can't submit two forms with the same button. You'll need to combine the two fields into a single form.
You can move the file input to the first <form> (which btw, you haven't closed) and use javascript to check if text has been entered and file has been selected.
Don't nest your form tags (It's invalid HTML). You can place all the inputs in one form so they are posted together.
e.g.
<form enctype="multipart/form-data" action="xx.php" method="post">
Enter Title of the Post<INPUT type="text" name="title">
<br/>
Enter Description
<textarea rows="10" cols="50" wrap="physical" name="post">
</textarea>
<br/>
<br/>
<input type="hidden" name="MAX_FILE_SIZE" value="1000000" />
Choose a file to upload: <input name="uploaded_file" type="file" />
<input type="submit" value="Upload" />
</form>
Oh, as a sidenote, you may not want to use a name like "post" in your input control.