and better to download directly from google play because the apps from google play store are legally verified and updated. without wasting much of your time let me give you the guide.
how can i download from play store to my pc?>> you have to download apk downloader for firefox here and for chrome here
run and install the apk downloader on your browser,its an add-ons.
once downloaded, go to play.google.com search for any app you want to download you should see something like this
now click on the download you will be redirected to a page with this window,
here or dial *#*#8255#*#* it opens Gtalk service monitor, but if the code doesnot work for you download device id apk to your phone.
once the above is completed you can now go to play,google.com at any time with you pc to download any apk file you want to do download on your browser.