As a part of your app marketing strategy, you should have a Facebook page. For it, you will need to create a profile picture and cover image. In this instructable, we'll show you the simplest way to do it.
First, Visit Placeit.net and choose a mockup.
Step 1: Create Your Mockup
Then, upload a screenshot of your app or choose "Grab Screenshot From URL" if you want to show a website. Make sure to choose a mockup image with a widescreen format. A square mockup will be harder to crop to the Facebook cover size.
Step 2: Access the Image Editor
Instead of just downloading the mockup, choose "Add Effects". It will ask you to download the image. Choose the middle or right options (High and Super High). This will open the image editor that will allow us to crop and resize the image to fit the Facebook cover size.
Step 3: Resize the Image
The Facebook cover size is 851x315 pixels. To resize the mockup, set the height to 315. You'll notice that the width 892 instead of 851, but we'll crop that later.
Step 4: Crop Your Image
Now, access the crop feature and select 851 as your width. This will show a rectangle you can reposition to crop the image to your liking. When you're done, click Apply and then Save. Your image will be downloaded.