You can use a config for it if your site is one language or you can use a translation file for it
I will go through both.
For the config we need to add a new value to the config/app.php file or even create a new config file, that's up to you. This should be added like an array, so we can simply do this
// config/app.php
<?php
return [
'name' => 'My Application Name',
// The rest of the configs.
];
Now you can access the name like so in your code and your views
config('app.name'); //My Application Name'
// And for your view
<h1>{{ config('app.name') }}</h1>
Using a translation file is just as easy as the config file. You simply create a new config file and then add the following
// resources/lang/en/app.php
<?php
return [
'name' => 'My Application Name',
];
If the application language is set to 'en' you can access the value like so
trans('app.name');
Now for each other translation you just create the new name.
We already discussed the config part, but if you think your application name might change in the future, you can put it in an environment variable like so
// .env
APP_NAME=My Application Name
And you can put this in your config, so you can change it depending on the environment of the application (you might have multiple deployments, just as an example)
// config/app.php
<?php
return [
// We use the .env if it exists or display the default value
'name' => env('APP_NAME', 'My Application Name'),
// The rest of the configs.
];