Hi @mrhunter46300
Here's the [https://h10032.www1.hp.com/ctg/Manual/c03231389.pdf|maintenance and service guide] for the laptop.
Go to p.38 (p.46 of 104 pdf numbering) to view the procedure to remove/replace the memory modules.
The laptop support up to 8GB of memory in 2 slots i.e. 2 x 4GB.
If upgrading to 8GB ensure that both memory modules are identical to avoid any compatibility problems.
Search online for [https://www.google.com/search?client=firefox-b-d&q=2+x+4GB+PC3L%2C+12800%2C+1600+MHz+memory|2 x 4GB PC3L, 12800, 1600 MHz memory] to find suppliers that suit you best. (examples only)
Alternatively search online for [https://www.google.com/search?client=firefox-b-d&q=641369-001|641369-001]