Re: can i send pictures from my desk top to my 6S plus
Yes, either enable iCloud Photo Library or photo stream on both your computer and your iPhone 6S. The pics should sync. Alternatively, you can send the pics via iTunes or a cloud service like Dropbox, OneDrive, etcetera.
You can also use airdrop to accomplish this. I downloaded a free app from both the mac app store and iOS App Store called DeskConnect that easily let's you share files between the devices. Works better than airdrop IMO.
Airdrop is the best option, if you dont have a mac then there are some other apps like instashare that let you send photos and documets over bluetooth. I had the mac version of instashare when there was no airdrop, it worked well.