How can I transfer files from computer to iphone?

Firstly, it must be noted that you cannot install/transfer ordinary Windows applications onto an iPhone. The iPhone has specially designed applications that are available to download directly from your phone using the "App Store" or from the iTunes Store on your PC (which could then be synced to your phone).

Using iTunes, you can transfer/sync various music, video, photos onto your iPhone by adding the respective files into the iTunes library and then having them synced to your phone automatically or you could just simply "Drag and drop" the files onto your iPhone within iTunes.

To transfer documents and other files onto your iPhone, you would need to use applications such as "Dropbox", "USB Disk" which are available free of cost in the App Store. Using these apps, through iTunes, you can also add different documents and files onto your iPhone for storage, however, it must be noted that these applications just act as a medium where you can store those files on your iPhone. The respective files actually may not open on your device itself.

Once you have downloaded those applications on your phone, you can open iTunes, click on your device. Choose the Apps tab and at the bottom you would see "Apps File Sharing". You can then add your respective files into those applications (Which would indirectly mean they are being stored on your iPhone)

Though it may all seem a little complicated, with a bit of usage, it's fairly easy to get acquainted with the iPhone. Do get back to us for more help!