After the theme is installed, you can install the plugins. Cmsmasters themes usually come with the following plugins included in the archive:

Contact Form Builder
Revolution Slider
LayerSlider WP

Also some themes come with WooCommerce plugin.

All the plugins are located in the "Plugins" folder of your archive and allow you to add contact forms and use our shortcodes, and were elaborated specially to avoid slow theme loading.

You can do it using your FTP client - Filezilla, FireFTP, etc. - or hosting C-panel.
Open a drop-down menu by clicking the right mouse on the folder, specified above.
Choose there "access rights" (or maybe something similar - depends on your FTP client) and make changes.

Don't apply this action for the subfolders and nested files.
Also, please, don't set the "777" permissions to "wp-content" folder or the whole theme folder for security reasons.

To add the plugin, please, proceed:

install-6

Then proceed to Upload tab:

install-10

Then choose the .zip folder with our plugin, and upload it. Once it will be added to the menu, you may enable it:

install-7

You may also unzip plugins to the following folders, appropriately:
wp-content/plugins/contact-form-builder,
wp-content/plugins/revslider,
wp-content/plugins/LayerSlider
wp-content/plugins/woocommerce (if your theme comes with it).