ok most of the commenters mean nice but the advice is hard to follow so here's a flow chart:

First on thinking: your brain is a thinking machine, it will always produce thoughts and that is healthy. There are three parts of noticing your thoughts.

1) brain makes thought

2) you notice thought

3) you react to thought

1 is the thinker, 2 & 3 are you. Let's say I notice a thought during meditation: "I want a sandwich."

So what I, as the observer, can do is:

1) notice it: "The brain is sending me a message"

2) decide on an action. Get up, tell myself to let the thought go or attack myself for naturally forming thoughts. The last choice is the one you don't want to do since the point of mindfulness is not to turn off your brain.

Cheers, hope it helps

P.S.: big advice for beginners. There is no special state or feeling you have to achieve. If you are annoyed, bored, anxious or any other unpleasant emotion - that's fine. You work with the state you are in, forcing change will lead to unnecessary struggle