Of course, it has been a culture that no one really dares to talk about learning these things publicly or positively, more or less like for you to learn it through see-and-poke trials. But of course, being a curious person in nature, you might end up not knowing if the trials and errors you're doing is on the right track.
Author's note : No matter how it comes to, a walkthrough is still a walkthrough, and being yourself, knowing what you are doing is important.
A typical pack of condom would look like this. So do not worry if it looks different from what you usually see in oversea's movies. A normal pack would gives you 3 of this thing and with a manual/instruction with it. There are different variation that you can see from shops, and it's available worldwide on your beloved convenience store (eg. 7 Eleven).
Have the condom's tip facing upward (outside/opposite) of the private part before inserting it in.
Again, the representational subject, and the closest, would be this at this angle and shot. Just make sure it's fit and you are in a comfortable position.
And when you have ejaculated, make sure you hold the condom properly and remove it from the tip. Wrap the remains properly before disposing it. And, no, please do not throw it inside the hole of the toilet, you'll create a blockage in the water system. If you afraid and doesn't want people to notice you're using it. Wrap it with papers/tissues.