PCI EXPRESS x16 Graphics Card

Hey Guys,

                    I own a HP AIO Desktop- HP Pavilion 23-b026in which has a Nvidia Geforce 610 graphic card which is soldered onto the motherboard. I want to upgrade my graphics card but since its soldered I cant upgrade it so PLEASE can anyone shed some light on What is PCI EXPRESSS x16 Graphics card slot? How can I use it? Will it increase my graphic processing power or any other alternative so that i can upgrade my graphics power since I want to play Watch Dogs.

Here is my Desktop Specification link:

http://h20566.www2.hp.com/portal/site/hpsc/template.PAGE/public/kb/docDisplay?javax.portlet.begCacheTok=com.vignette.cachetoken&javax.portlet.endCacheTok=com.vignette.cachetoken&javax.portlet.prp_ba847bafb2a2d782fcbb0710b053ce01=wsrp-navigationalState%3DdocId%253Demr_na-c03546694-7%257CdocLocale%253D%257CcalledBy%253D&javax.portlet.tpst=ba847bafb2a2d782fcbb0710b053ce01&sp4ts.oid=5295897&ac.admitted=1401804097938.876444892.199480143

Here is my Motherboard specification link:

http://h20566.www2.hp.com/portal/site/hpsc/template.PAGE/public/kb/docDisplay/?sp4ts.oid=5295897&spf_p.tpst=kbDocDisplay&spf_p.prp_kbDocDisplay=wsrp-navigationalState%3DdocId%253Demr_na-c03340922-5%257CdocLocale%253Den_US%257CcalledBy%253D&javax.portlet.begCacheTok=com.vignette.cachetoken&javax.portlet.endCacheTok=com.vignette.cachetoken