I guess first I need to ask the obvious questions.
Is the battery fully charged?
You are sitting fully in the seat?
The mower is fully disengaged?
The brake pedal is pressed all the way down?
Even a new battery must be charged, they do not come fully charged.
When you turn the key to start, do you hear a click or anything?
Do you have a multimeter (preferably) or a test light available?
when i turn the key all i hear is a one click.
No. i don't own a multimeter or a test light.
We can do some testing. If it turns out to be mechanical, we can figure it out, but if it is electrical, you will need a meter or a light.
First, check your oil level and make sure it is not overfull.
Smell the oil. If it smells like gas - stop there.
If the oil level is good and does not smell like gas, remove the spark plug and see if the engine will turn over then.
Let me know what you find.
If it was a safety switch, you should not hear a click at all, so I am not believing this is your problem.
It is very possible it is the solenoid itself.
It is also possible the battery does not have enough voltage in it to turn the starter.
Assuming the battery is OK, one way to test the solenoid is to use a piece of cable or very heavy wire and jumper across the 2 large posts of the solenoid. If the starter does not engage, the battery is at fault.
If the starter does engage, it is in the control system or the solenoid.
Using a test light is simple - you just connect the ground clip to a good ground and test for input/output voltage at the various components. However, a meter is much better as it will actually tell you whether or not you have enough voltage present. A light will only tell you if voltage is there - it will not tell you if there is insufficient voltage.