You can use SleekBoxes on as many pages as you like.
What you need to consider first: Is all your websites under the same domain?
If your website(s) are under the same domain, you only need to insert the tracking code once.
The tracking code can be found here:
When creating a SleekBox you simply enter the URL of your website (homepage):
When you have created your SleekBox you can then decide what page it should be shown on. You do that by navigating to "Settings" on the lower right corner of the screen:
Here you have the option of setting up where the SleekBox will show. You do that by adding a condition:
You must pick "Specific URL" and here you have the option to show it on a page in another language.
For example: If you have a Danish version of your website it could be yourname.com/dk or if it is a German version it could be yourname.com/de
Now this particular SleekBox will only show on the Danish version of the site.
What if my website(s)/page(s) have their own domain?
You simply create a SleekBox, and in the very first step simply enter the URL. If it's your German version a ".de" is sufficient. Remember: It depends on your domain name.
Remember if you have more domains. For example: "yourname.de", "yourname.dk" and "yourname.com" you need to insert the tracking code on each website.