I am able to download and upload plugins and activate them this way, but for visual composer, i cannot activate the free trial due to soe sort of permission issue i believe. I am looking for two solutions.

1. How do i install the plugins directly from the theme itself? It just says failed to install xx theme.
2. When i upload the most important theme Visual Composer, and try to activate free trial version, it would not let me due to possibly permission issues.

Please help!!

Thanks much

PS: Lamp stack self hosted server