I have got a profile and signed in, but I cannot see any instruction as to how to follow the course
On the unofficial wiki, the Getting Started Guide is probably worth a read first. http://duolingo.wikia.com/wiki/Getting_started
But really, all you need to do is click on the skill circles, click begin on the lessons, and work through them. The words in the lessons can be hovered over to get hints, and if you get an answer wrong it will (normally) tell you what the answer should have been so you have more of a chance of getting it right next time. The course is very much about the hands-on exercises.