There are a couple of ways to trigger a commit command in Solr. The easiest way is via a URL:

http://localhost:8983/solr/collection1/update?commit=true

(Replace localhost:8983 with your Solr url and )

But you can also commit using the Documents option from the Admin UI. Simply navigate to Documents, using this URL:

http://localhost:8983/solr/collection1/documents

And select Solr Command (raw XML orJSON), adding the command

<commit>
true
</commit>

Submit Document! It just works. And if you are using SolrCloud, the command goes to everyone.