Hello @Alon14,
You can change your standard nightly price as follows.
Go to your calendar and click on "Manage settingds" in the top right hand corner.
Then click on "Pricing".
In the "Nightly price" section click on the "Edit" button and set your base price.
On that "Pricing" page you'll also see sections where you can set discounts and extra charges.
You can change prices for individual dates or a range of dates as follows.
Go to your calendar and click on a date. A box will appear on the right. Set the start and end dae and the price you want for that range of dates and then click "Save changes".
Steve.