In order to create a template, you start a new article, and naming it like this: [[:Template:New Template]]. All the content in that article will then be easily transcluded to any other page through using the code to call it in: <nowiki>{{New Template}}</nowiki>. That template article content will then replace the "<nowiki>{{New Template}}</nowiki>" snippet. Check our [[Help{{WikiTitle}}:Policy|title naming policies]] for further help.