Hi Danny,
I find the easy way for me is the do a general google search. eg, song called 'your latest trick'...can be anything but this is for example. at the end of the title of song you are searching for, add the term 'midi'.

so your google search will look like this. your latest trick midi. search try what ever one takes your fancy. note . these are some version better than others if you are going the 'free midi' route.

when you have found what you like, if it plays in quicktime, at the right hand side of the playing bit, you see a drop box box arrow. click on this and select 'save as'

you can then save this midi file to a file on your pc. as you are new to this, may i suggest you first create a file and call it my midi files as a start point. you can be more creative as you gain experience.

going back to the point you are at save as, it will show all files on your pc. select your file'my midi files' and save. it saves to this box.
back to notation. click on 'file' top left prog- open- search for your 'my midi file' folder. open the folder, it will show your new downloaded midi file - your latest trick. doulble click on this and there you are.
hope this helps.

you can buy midi files and these are generally better quality. however, the free ones aren't bad and you can if you know how, tweak them to show better. we use free midi's and gigged for many years using them.

And finally...I remember being told at an early age, there is no such thing as a stupid question, just stupid not to ask it. if you get stuck, drop me a line.

all best
andy