composer.json is not in "Getting Started" as promised in error message.

[roger2]

error ....................
To initialize a project, please create a composer.json file as described in the https://getcomposer.org/ "Getting Started" section


How do i create " composer.json "

I'm stuck at "installer"  ..... "elinks  host/roundcube/installer"  displays locally but not remotely.

Got to be something simple.

all help welcome

[roger2]

found the howto here ..OK now

https://github.com/roundcube/roundcubemail/wiki/Installation