How can I upload my pictures to the iCloud

If you mean photo stream, go to Settings>iCloud, sign in with your Apple ID to create your iCloud account, tap Photos and turn on My Photo Stream. Then photos you add to your camera roll, such as photos you take on your device will automatically be added to photo stream when your device is connected to wifi with the camera app closed and with at least 20% battery life remaining.

Note: only photo added to the camera roll after enabling my photo stream are added to your photo stream, not existing photos.

No. If you add them to iCloud, either to your photo stream or to a shared stream, then delete them from your phone they will also be deleted from iCloud. This is likely to change this fall with iOS 8, which will include iCloud Photo Library (http://www.apple.com/ios/ios8/photos/) to host all your photos. But at the present time, if you want them off your phone you'll have to either import them to your computer and delete them (see http://support.apple.com/kb/HT4083) or use another cloud service such as Dropbox.