Hi there,
Thanks for writing in!
You can install those plugins/ extensions manually by uploading it to you server. In the main X Theme folder that you download from Themeforest, locate the zip files under the Plugins folder (“X/framework/plugins/“). Then Unzip each plugin files and use a FTP Client software (FileZilla Client) to upload it into your server (ROOT/wp-content/plugins/) folder.
Once you have uploaded it into the server, login to your WordPress back-end and head over to the Plugins -> Installed plugins to activate those plugins.
Hope that helps.