I. MAGENTO 2 INSTALL EXTENSION
As you may know, there are two most popular ways of installing magento 2 extension. The first one is to use COMMAND LINE and the send one is to install manually.
Option 1: Magento 2 install extension using COMMAND LINE (Recommended)
Your magento 2 extensions can be installed in a few minutes by going through these following steps
Step 1: Download/purchase the extension
Step 2: Unzip the file in a temporary directory
Step 3: Upload it to your Magento installation root directory
Step 4: Disable the cache under System >> Cache Management
Step 5: Enter the following at the command line:
php bin/magento setup:upgrade
Step 6: After opening Stores >>Configuration >>Advanced >> Advanced, the module will be shown in the admin panel
Option 2. Magento 2 install extension manually
Step 1: Download/purchase the extension
Step 2: Unzip the file in a temporary directory
Step 3: Upload it to your Magento installation root directory
Step 4: Disable the cache under System >> Cache Management
Edit app/etc/config.php file and three line code:
‘Ves_All’ => 1,
‘Ves_Megamenu’ => 1,
‘Ves_Setup’ => 1,

Step 5: Disable the cache under System >> Cache Management
Step 6 : After opening Stores >> Configuration >> Advanced >> Advanced, the module will be shown in the admin panel.
>> UPGRADING DATABASE
If you need to upgrade the database, run the following command line:
php bin/magento setup:dbschema:upgrade
Ref: landofcoder