We will go over installation of Conversations app that will be similar to this video.
Conversations is a chat application that runs on Android and uses the XMPP protocol. There are a lot of different XMPP apps that run on different platforms and devices, and thanks to this protocol users can communicate with each other regardless of the device or operating system they are using.
Unlike most mainstream chat apps, Conversations is not run by a company. It's code is open source, fully available online for anyone to read, modify or share. That means that it is developed with only the user's interests in mind, since anyone can just change the code and share it if an unpopular feature is added. This way nothing in Conversations will harm or inconvenience users. Common practices such as collecting personal information to sell to advertisers and adding addictive features to try and keep users attention do not exist in Conversations.
Furthermore, there are no central servers run by the developers. Anyone may be a developer and anyone may run a server for Conversations.
There are multiple ways of installing Conversations, but the best way is to install it using the F-Droid app.
F-Droid is a transparent and privacy respecting alternative to Google Play. Since Google Play doesn't allow competition, F-droid can not be found in Google Play store and has to be downloaded from the F-Droid website at f-droid.org.
First, download F-Droid.
Install it on your Android device by clicking and opening the downloaded file.
Open your newly installed F-Droid app.
You will need to wait a few minutes while it is updating the list of available apps.
Now you can install the Conversations app.
Click the search (spyglass) button at the bottom right of the screen.
Type Conversations in the search bar that pops up at the top of the screen.
Sometimes it will not show up as the top result, and you may have to scroll down find the app. If you have scrolled all the way down and still do not see the logo shown in this article, click on a result that matches the query, and make sure to check the images in the description for the app logo.
Don't worry about this, it's a useful feature that prevents unwanted software from being installed on your device, but it also means that any app that's not downloaded through an official app store will be flagged, as we've discussed at the beginning of the installation section.
After the installation you can open Conversations from the F-Droid app.
You can also open it like any other app on your phone.
Unlike most apps, Conversations lets you choose which server you will create your account on. You can run your own server, connect to a server of your local hackerspace, or just pick a random server suggested on this website. This works the same way as e-mail, where you can pick your e-mail provider or run your own server.
Some servers allow you to create a new account by choosing the "Create a new account" option when you open Conversations for the first time, but most servers have a website where you can create an account. 
If you choose the "Create a new account" option, don't use the server of conversations.im that will be suggested to you. It is safer to pick a random server than for everyone to use the same one. We don't want our communication to be fully dependent on a small group of people, like chat applications run by companies.
Go to the website of a server of your choosing and follow the instructions.
Once you have your address and password, go back to Conversations, and tap the "I already have an account" option.
Enter the address and password of the account you created.
Now you're ready to use the app.
To join a group chat you can tap the plus "+" button in the bottom right corner of the app window.
Some group chats are public, which means anyone can join. Others are private and you need to be invited to join.
To join the Decentrala public chat you can tap the "Join public channel" button and type "email@example.com"