copying open wifi networks/hot spots

ok,i was wantin to be able to save some wifi networks i have to a flash drive or to my home pc,is there a way to copy an open or a hot spot to a devise of some sort so i can always have wifi,for example,theres a library & a Walmart neighborhood market near me,can i copy a pice of there wifi to a devise so im able 2 have it all the time,or if i can copy this mobile hot spot device that the library were i live is doing,please let me know asap