A picture that looks good on your phone probably won't look good in print. Every picture is made up of pixels or dots. A phone is less than 1000 pixels wide and our brains have become accustomed to filling in details. Our brains don't do that with print, so we need to use more pixels AND we generally want to print bigger than a 10cm wide phone.
Whilst we don't offer creative design services, we do offer a range of affordable technical services to make sure your own ideas look good in print.
If you'd prefer to DIY, we strongly recommend https://www.canva.com/ . When you download your finished design, make sure you select PDF print and tick the cropmarks and bleed box. If you're using Canva, please see our artwork guide for more information