There are two ways to install a plugin on WordPress.
The easiest way is to install it directly from the backend. In some cases the installation may fail, so you have to install the plugin using FTP software.
Install from WordPress
Click the “plugins” link in the WordPress sidebar, click the “Add new” button, then the “Upload Plugin” button.
Use the file upload field to upload the plugin file name “wp-estimation-payment-forms-builder.zip” .
Once the plugin upload finished, activate it by clicking the “Activate Plugin” button .
Install from FTP
You require a FTP software like Filezilla to be able to upload a plugin directly on the server.
Your server has a FTP account (host,username,password) that was used to install WordPress onside and that will be necessary to upload the plugin.
First open the “wp-estimation-payment-forms-builder.zip” plugin file and extract its content.
Once connected to your server thanks to the FTP software of your choice, go to the folder “/www/wp-content/plugins/”, open it and copy the folder “WP_Estimation_Form” inside.