Homestead Bootcamp Windows 10 Spark installation -how?

I have finally managed to set up Homestead on my Bootcamp Windows 10 OS and have a test laravel 5.3 app running. I've purchased spark and I'm confused about how to proceed. Do I install it through Homestead or no? Can I use the 'spark new project' command or do I install a laravel instance and run composer update? I've tried both approaches with no luck, running into various errors -

If I try 'composer update' outside of homestead I get a 'you must enable the openssl extension in php.ini' error message.'

If I try 'composer update in homestead I get

    Now trying to download from source
  - Installing laravel/spark (v2.0.10)
    Cloning 4593d1cb56e21c2b802ef29961a1dcf34846a70a


  [RuntimeException]
  Failed to execute git clone --no-checkout 'https://***:***@github.com/laravel/spark.git' '/home
  /vagrant/Code/myapp.dev/vendor/laravel/spark' && cd '/home/vagrant/Code/myapp.dev/vendor/larave
  l/spark' && git remote add composer 'https://***:***@github.com/laravel/spark.git' && git fetch
   composer
  Cloning into '/home/vagrant/Code/myapp.dev/vendor/laravel/spark'...
  remote: Repository not found.
  fatal: repository 'https://***:***@github.com/laravel/spark.git/' not found

I'm guessing this last approach is the right one - I should be using a token, but how do I set this up? Spark installation guide says that I should be prompted about where to get one but this doesn't happen and instead tries the token you see above.