How to put pictures from my pc on my iphone 4s?

Hello Benghea,

It sounds like you would like to sync photos from your Windows computer to your iPhone. You can do this in iTunes the same way you would with Music, but you would click the Photos tab when you have the device selected in iTunes:

iTunes: Syncing photos

http://support.apple.com/kb/ht4236

To sync photos from a folder on your computer to your device

1. Place all of your photos into a folder on your computer. You can organize photos into subfolders to make albums.
2. Select "Sync Photos from."
3. Select "Choose folder" from the pop-up menu and choose the folder where you stored your photos.
4. Click Apply.

Thank you for using Apple Support Communities.

Take care,

Sterling

Will it replace all my other pictures on my iphone or just add in the news ones from my computer, if I use the itunes sync?