1. Go to Main_iPhone.storyboard
2. Press control + alt + cmd + 3 to show the object library on bottom right.
3. Search for bar button item. Drag it to the desired place in toolbar inside storyboard.
4. Each bar button item must have a flexible space bar button item around it. Drag one to the right place.
5. Press alt + cmd + enter to show assistant editor and set it to automatic and open ViewController.h there.
6. Ctrl + drag from new bar button item to the ViewController.m on the right at the end of the file but before @end statement.
7. A popup will appear. Select Action in Connection dropdown and name the connection and hit connect.
8. A new line will be added with a double dot on its left.
9. Now go to ViewController.m and search for the string newItem. This is an IBAction where you can write the logic to be performed when anyone click this button.
1. Click a Bar button Item and press alt + cmd + 4 to show the property inspector on the right. There is an image field which has name of the image. Note that name down.
2. Go to image.xcassets and find the image. Replace the images by draggin and dropping to the thumbnails from finder. The icon must be in 3 sizes 30x30px (1x) 60x60px (2x) and 90x90px (3x).
3. Add and image in images.xcassets by clicking the plus icon in the left bottom and then selecting New Image Set.
4. Rename the new image by single clicking on its name. Also drag and drop icons of same size as done in step 2.
4. With the new bar button item selected, press alt + cmd + 4 and clear out the title field. In the image field type the name of new image you just created to change the icon of new bar button item.