I read all this information using Git, packageist website. I have little knowledge but growing. Here is what im trying to do. Upgrade my website which is obviously not on either of those sites. My question is do  I use composer to upgrade elgg on my server (Obviously). How ? I have seen so many scripts such as the following.

composer self-update
composer create-project elgg/starter-project:dev-master ./path/to/project/root
cd ./path/to/project/root
composer install
composer install # 2nd call is currently required
vendor/bin/elgg-cli install # follow the questions to provide installation details

1: I have no idea what to do for instance. Where do I download the next Elgg site on my local computer so that I can use composer to upload to the server where my website is located. 

2: In this script ti doesnt say where to upload the files so where do i tell it so it can look for my server, and how do I code it. 

THank you