How to post on reddit?

You're probably having issues posting to a particular 'sub-reddit'.  many of them have rules you must follow and formats for the title etc.  For instance, r/explainitlikeimfive each title must be started with ELI5: including the colon.  Each time you go to a sub, or want to post in one, take a few moments to read the rules for each one.  

There's a big bar at the top you can post your question at kind of looks like a search bar, also the pencil at the top right.