For fixed price projects, you can edit a project's base contract price from the project's Financial > Estimate page if you're tracking your budget.
If you're not tracking your budget you will find this on the project's Setup page.
You can get there by going to the Main Menu > clicking the "i" info icon next to the project > Edit Project Setup.
On the Setup page, you will see the price and you can make any necessary changes.
On open book projects, you will see the starting and total price of the project. The starting price will be set based on the estimate and spec/selection information that you set up, since the client's overall price will be a function of your actual costs, plus markup.