How will GLPI deal with composer when installing?

Question

linux

Good day.
I'm trying to install Glpi 9.2.2 on UbuntuServer 16.
After configuring LAMP and composer on the server page in the browser, I see the message:
"Run "composer install --no-dev" in the glpi tree.
To install composer please refer to https://getcomposer.org/”
Then I follow the instructions to perform this action on my server, but in the end it comes out. I can't figure out what he wants from me. Who can faced similar?