On Joomla you will just have to download the package and install it on your website, it will automatically update it without losing any data:
Browse for your AcyMailing package and then click Upload & Install.
You can also use the Joomla update system for paid versions if you attached your site to your license:
Then click on Find Update if they are some check it and click in Update
The old version 5 of AcyMailing isn't on the WordPress plugin listing site, which means that it isn't available in the Updates page.
As WordPress doesn't do the plugin update if you try to install the new version over a previous one, you will have to follow these steps:
Backup the folder wp-content / plugins / acymailing5 / media / upload /
Remove the folder wp-content / plugins / acymailing5 /
Install the new version of AcyMailing 5 on your WordPress website, using the Plugins => Add New => Upload Plugin option of WordPress
Add back the folder wp-content / plugins / acymailing5 / media / upload /
If you're unsure, you can backup the folder acymailing5 before following these steps.