Hi I am trying to create a site. I go to Site Action> Create site> I have a costum template that I am spose to use. but I cant create a defualt page in it? what should I do?

Is this for a publishing page? By custom template do you mean a custom page layout? Or do you mean a custom master? The master will inherit from parent. Otherwise, create the subsite, then, in the toolbar go to Page>Page Settings and Schedule>Locate the Page Layout section and change to your custom page layout. I'm answering based on an assumption that this is a layout and for a publishing site. Please clarify if that is not accurate.

That the thing how can tell! in the tamplate that I can select when creating a new site. I have a custom one that I should use. But then in is not letting me create a page in that site. is there a way around this? or should I just use other templates?

Is this template for the WSS side or the Publishing side? In other words, is the "Office SharePoint Service Publishing Infrastructure" feature activited under Site Collection Features? If you are unable to tell this... when you create a site, are the templates you want to use under a tab called "Collaboration" or under a tab called "Publishing"? If you are working with the WSS side (Collaboration), from the sounds of it, it seems like what you need to do is take your custom template and upload it to the Site Template Gallery so that it will be available for you when you create the site. If you are working with the Publishing side, you need to get your page layout loaded into the master pages and pag elayouts gallery. I hope this is helpful.