Q: Mid 2009 13 inch macbook white ram upgrade

You can use this Link to check which RAM is suitable for your Mac...

http://eshop.macsales.com/shop/apple/memory/

It is Important to get the Correct and Matching RAM

For best performance, fill all memory slots, installing an equal memory module in each slot.

That site also has videos on how to Install RAM should you need it...

Here are Apples Instructions... Installing RAM

MacBook  http://support.apple.com/kb/HT1651

RAM specs below.

Maximum Memory     6.0 GB (Actual) 4.0 GB (Apple)

Memory Slots     2 - 200-pin PC2-6400 (800MHz) DDR2 SO-DIMM