Fertile window

Renz • ? 2015 ?
Hi all I'm new to glow .. 
​Myself and my partner are TTC I use to use a different app but lost all my data ? .. So I've downloaded this app and hopefully I shouldn't have any problems .. (Sorry for waffling ) 
​Question ... How soon after you AF does your fertilily window start???? 
​I'm trying to go off memory from my pervios app so I can input my information on glow, but glow prediction seems to be a tad different someone pleas help me! ?