By default, every users in your organization can go to Microsoft Teams apps store to install Yeeflow individually. After the Yeeflow is installed, users can see and access Yeeflow from the installed apps list.
This needs everything to do the installed by themselves. However, if you are the admin of your Office 365, and you want to install Yeeflow for your organizaiton automatically. You can use app setup policies to customize Microsoft Teams.
You choose the apps like Yeeflow to pin and set the order that they appear. App setup policies let you showcase apps that users in your organization need, including those built by third parties or by developers in your organization. You can also use app setup policies to manage how built-in features appear.
Apps are pinned to the app bar. This is the bar on the side of the Teams desktop client and at the bottom of the Teams mobile clients (iOS and Android).
You manage app setup policies in the Microsoft Teams admin center. You can use the global (Org-wide default) policy or create custom policies and assign them to users. Users in your organization will automatically get the global policy unless you create and assign a custom policy.
To set up the global policy, you need to firstly login to you Office 365 admin center with the Office 365 admin account. Then from the left menu, select "Teams" under admin centers:
Then in the Teams admin center, select "Teams Apps - > Setup Policies" from the left menu. You can edit the settings in the global policy to include Yeeflow. If you want to customize Teams for different groups of users in your organization, create and assign one or more custom policies. If a user is assigned a custom policy, that policy applies to the user. If a user isn't assigned a custom policy, the global policy applies to the user.
Click "Global (Org-wide default)", you will see all the pinned apps in the list:
Then click "Add Apps" button, in the pop-up window, select "Global" in the permission policy list, and search "Yeeflow" in the search box. From the search result, click "Add" button to add Yeeflow to the pinned apps list.
Then in the pinned apps list, you can see Yeeflow is already added. You can select it and change the orders, and click "Save" button once you are done.
Once you get all those steps set, next time if anyone in your organization login to their Microsoft Teams app, they will see Yeeflow from the main pinned apps list.
You can also use the Microsoft Teams admin center to create a custom policy. And add Yeeflow app to the custom policy.
For more information regarding how to customize the policy and set up apps, you may check the reference link below: