I am on the https://jqueryui.com/selectmenu/ website where I am trying to build xpath for the first selector Select a speed. I build the xpath to iframe but how to reach the first selector Select a speed?
//body/div[@id='container']/div[@id='content-wrapper']/div[1]/div[1]/iframe[1]
Since your elements are inside the iframe in order to access these elements you should first switch to the iframe as described here
Also, to locate the iframe you can simply use one of the following xpaths//iframe or //iframe[@class='demo-frame'] or select by class demo-frame etc.
After switching into the ifame the xpath to select a speed is //span[@id='speed-button']
