You might not be able to see a dataset page at all, even though it exists. This might be because its owner has removed your access or added extra steps to gaining overview access that you haven't completed yet. Contact the owner of the dataset to get started.
You can see the dataset page and view the access application. You will not be able to see any information about specific variables or data.
This is an optional access level which might only be applicable to some datasets. If a permission group has requirements at this level, once completed you will only have data access to the 1% sample until you complete all requirements on the Data access level. At that point you can switch to using the full dataset. If a dataset does not have a sample, you will be able to access the full dataset when you gain any level of data access.
You can edit the dataset and its contents by clicking the Edit dataset button in the usage box on the right side of the dataset page. If the dataset is owned by an organization, you must be an administrator to have edit access. If the dataset is owned by a user, that user can grant you edit access directly.