The topic of that link (install the PAE kernel) is almost certainly what you need.
But in that link there is some very careless phrasing
The non-PAE kernel can only address up to 4GB of memory. Install the kernel-PAE package if your machine has more than 4GB of memory
That part is misleading (and contradicted by other phrases on the same page).
The correct information is:
The non-PAE kernel
can address up to 4GB of physical address space. 4GB of physical address space can contain only 3 and a fraction GB of actual memory
(the exact amount is determined by the BIOS, not by Linux).
Install the kernel-PAE
package if your machine has more than the 3 and a fraction GB
of memory that fits in 4GB of physical address space.