Welcome to the DNN Community! You can definitely add a customized page to your website, but first it may be helpful to understand more about how DNN is architected. The reason I say this is because "custom" could mean different things to different people. It could mean a custom design (theme) or custom functionality (modules) or customized access to the page (permissions). 

DNN has "separation of concerns" meaning that the design is distinct from the content. A designer/theme developer can create any look and feel and layout they want and not worry too much about which modules get injected into the page. Likewise module developers can build out extensions and not worry too much about the design because the theme developers are handling that portion. 

So the main question is what do you mean by "customized page" ? 

If you're referring to a custom design then check out:

 - DNN Skinning Wiki
 - DNN Video Page (Design Section)

If you'referring to a custom module then check out:

 - DNN Module Development Wiki
 - Module Development For Beginners Blog Series 
 -  DNN Video Page (Module Development Section)

If you're referring to DNN's permissions model then check out:

 - Granular Permissions in DNN Video