Cost Calculator Builder WordPress plugin has two types, basic free, and pro versions. According to the version of it, the installation process will differ.
As it is a WordPress plugin, you can install it in two ways following:
In a first way, download the plugin archive file here https://wordpress.org/plugins/cost-calculator-builder/
Follow to Plugins > Add New from your dashboard.
Click on the Upload Plugin button and select the Cost Calculator Builder downloaded file from your local folders. Click Install Now and wait for the installation to finish.
After installing it successfully, you need to activate the plugin.
The second way of installation is done in your WordPress dashboard directly:
Go to Plugins > Add New from your dashboard and give a desired search.
From the results of search box, install the plugin. After clicking the Install button, Activate button will appear. Click it for activation.
When all your data is found to be correct about your buying, you will get a welcome message by Freemius sent to your email.
In that message, you will be aware of the link of Pro Plugin's download page with the license key to activate the plugin. You will also be informed with some personal data and instructions for activation.
Go to Plugins sections from your dashboard, then go to Add new and choose Upload plugin function from there.
Choose the given archived file from the local system where you downloaded. Then, click Install Now button.
Click Activate Plugin button. Then you will be directed to the activation board where you should paste the license key that you are given by Freemius.
Press the button Agree & Activate License to activate:
After activating successfully, you will be redirected to Cost Calculator Plugin dashboard to begin your work.