I just implemented that exact mootools script with weblogin on one of my modx sites located here -
http://www.vistartech.com/login-test
It’s quite easy to do. Simply follow all of the instructions provided with the script. Where the form html code goes replace it with your call to weblogin like so:
<div id="login">
[!WebLogin? &tpl=`FormLogin` &loginhomeid=`67`!]
</div>
The TPL file you specify in the weblogin call should look something like this:
<!-- #declare:separator <hr> -->
<div class="loginContent">
<form method="post" name="loginfrm" action="[+action+]"> <input type="hidden" value="[+rememberme+]" name="rememberme" />
<label for="log"><b>Usernames: </b></label>
<input type="text" name="username" id="username" tabindex="1" onkeypress="return webLoginEnter(document.loginfrm.password);" value="[+username+]" class="field" size="23"/>
<label for="pwd"><b>Password:</b></label>
<input type="password" name="password" id="password" tabindex="2" onkeypress="return webLoginEnter(document.loginfrm.cmdweblogin);" value="" class="field" size="23" />
<input type="submit" value="" name="cmdweblogin" class="button_login" />
</form>
<div class="right">Not a member? <a href="[~5~]">Register</a> | <a href="#" onclick="webLoginShowForm(2);return false;" id="forgotpsswd">Lost your password?</a></div>
</div>
<hr>
<!-- log out hyperlink section -->
You're already logged in<br />
Do you wish to <a href="[+action+]" class="button">[+logouttext+]</a>?
<hr>
<!-- Password reminder form section -->
<form name="loginreminder" method="post" action="[+action+]">
<fieldset>
<h3>It happens to everyone...</h3>
<input type="hidden" name="txtpwdrem" value="0" />
<label for="txtwebemail">Enter the email address of your account to reset your password: <input type="text" name="txtwebemail" id="txtwebemail" size="24" /></label>
<label>To return to the login form, press the cancel button.</label>
<input type="submit" value="Submit" name="cmdweblogin" class="button" /> <input type="reset" value="Cancel" name="cmdcancel" onclick="webLoginShowForm(1);" class="button" style="clear:none;display:inline" />
</fieldset>
</form>
<div class="loginClose"><a href="#" id="closeLogin">Close Panel</a></div>
Hope that helps!