WP-Juicebox (the Juicebox plugin for WordPress) supports only one gallery per page or post.
If you want to embed multiple galleries on a single page or post, you'll need to embed them manually.
I would recommend using the baseUrl method of embedding as documented here.
Essentially, once you have created a gallery with JuiceboxBuilder-Pro, you would upload the complete gallery folder (not just the contents) to your web server and paste the baseUrl embedding code into the body of your WordPress page or post (ensuring that the method of entry is 'Text' rather than 'Visual'). It does not matter where on your web server you upload your gallery folder to as long as the two paths in the embedding code (the path to the 'juicebox.js' file and the baseUrl itself, pointing towards the gallery folder) are correct.
As you have already uploaded a complete gallery folder ('jbox') to your web space's root directory, you can use the following embedding code. The leading slashes in the paths denote your root directory so the embedding code will work in any web page throughout your site without any modification (although you can change the gallery dimensions and background color if required).
<!--START JUICEBOX EMBED-->
<script src="/jbox/jbcore/juicebox.js"></script>
<script>
new juicebox({
baseUrl: '/jbox/',
containerId: 'juicebox-container',
galleryWidth: '100%',
galleryHeight: '600',
backgroundColor: '#222222'
});
</script>
<div id="juicebox-container"></div>
<!--END JUICEBOX EMBED-->
Notes regarding embedding multiple galleries in a single page or post
(1) Make sure that you embed each gallery into a container with a unique containerId/id.
(2) Load the 'juicebox.js' file only once per web page (not once per gallery).
For example, if you uploaded a second gallery folder ('jbox2') to your root directory alongside your current gallery folder ('jbox'), then you could embed the two galleries in a single page or post using the following embedding code:
<script src="/jbox/jbcore/juicebox.js"></script>
<script>
new juicebox({
baseUrl: "/jbox/",
containerId: "juicebox-container1",
galleryWidth: "100%",
galleryHeight: "600",
backgroundColor: "#222222"
});
</script>
<div id="juicebox-container1"></div>
<script>
new juicebox({
baseUrl: "/jbox2/",
containerId: "juicebox-container2",
galleryWidth: "100%",
galleryHeight: "600",
backgroundColor: "#222222"
});
</script>
<div id="juicebox-container2"></div>