For anyone stumbling upon this today looking for options, AdobeXD or Sketch are far superior to Photoshop mockups as they can be made client-side and interactable.
XD can be ported to a phone through the XD app, but fonts need to be installed on the phone to display correctly.
Adobe Comp is a mobile app that you can create mockups in on a phone (no pc ...
As Vincent has already said in his answer, the line is already present in the image. It looks as though it has already been badly edited. However, if you must edit this actual photograph and don't have access to a better unedited photo, then you can make it look a little better. It's not easy, and will take some manual retouching work.
I used the Select and ...
Use a text editor just change the font and color to the same value as the console your emulating.
A good editor can draw boxes and stuff, copy paste can make use of assets. If that's not enough use a ascii art tool. Obviously a text editor does not mean a word processor.