I need help with Video Card Configuration?

I just bought this ASUS EAH4350 SILENT/DI/512MD2 Radeon HD 4350 512MB 64-bit GDDR2 PCI Express 2.0 x16 video card and I can seem to get it to work right. Everything is running so slow and watching video online is a pain. someone help me please.|||your computer compatible with it? and/or maybe you need more ram?