I make a lot of my own graphics and one of the tools I use to remove a background from a photo is https://clippingmagic.com/
It's a very simple process and you can do a whole range of other photo editing. It's a subscription tool and at $4.99 a month for 15 edits I think that's invaluable. You can purchase 100 credits for $7.99 a month.
The photo above is a Facebook advert I created. I had to remove the white background from the photo of the man so I could change the colour of the background and add the other icons.
Here is the original photo I purchased it doesn't have a transparent background it's white. So unless I'm using white as my background it's not going to work.
To make my Facebook advert I cropped out the white background. I then uploaded it to my www.canva.com account. In Canva I chose the blue background for the advert and the font. I then found a colourful cloud in the illustrations supplied by Canva and placed the text in front of the cloud.
When creating Facebook adverts you can't have too much text compared to graphics so I utilise the text in the actual Facebook post to describe the service in more detail and a catchy header.