First of all, click the ‘Home’ button of your iPhone and unlock it by sliding your finger across the screen. This is relatively easy to do especially if you have been using your iPhone for some time now.
Then, find the ‘Clock’ app on your home screen and tap on it. Be careful to find your 'Clock' app as it might be sitting amongst other apps on your home screen.
Now, you will see some options at the bottom of your screen. Select the option ‘World Clock’ from those options.
After selecting the option ‘World Clock’, tap the ‘+’ button which will be displayed at the top right corner of your iPhone’s screen. It will show you a search box and it will display a keyboard.
You have to use the keyboard to type the name of the city which you want to add in your clock app. You will notice that it will give you the suggestions when you will start typing the name of your city. You can choose from the options or you can type the full name of your city by yourself. Be sure to get the spelling correct so that the right city is selected. If you do not find the city name in the given selection be sure to type the entire city name properly to make your choice.
Now, add the city to your list in order to save it in the clock app. Once selected you will have saved it to the clock app.
You can add more cities, if you want to, by repeating the same process. Just take your time and follow the steps for the different cities that you want to add.
Please keep in mind that the clock app will show the city in white colour where there is currently daytime. Moreover, the city where there is currently night-time will be shown in black colour. If you see ‘Tomorrow’ under the time of any city, it means that city is a day ahead of your city’s time. You can easily delete the name of any city, if you want to. Just tap ‘Edit’ option which is displayed at the top left hand corner of your screen, and then click the name of the city which you want to delete and tap ‘Delete’ button which is given at the right side.
If you face any difficulties then you can always go online and you will find a ton of websites or forums discussing various issues or tips and tricks from other iPhone users. You might even find an easier of doing some other mundane tasks as well. If you cannot find what you are looking for you can always post your own question in a decent forum online.