Hi and welcome to the forum. Not sure what kind of fretted violin you are using. I did take a look at the website The Fiddle Fretter (http://www.frettedfiddle.com/) and found this in the FAQs.
Do you place your fingers on the frets or behind the frets?
Try to place your fingertips just behind the frets. Preferably so you can FEEL the fret. This would be the exact position you should be in when not using the Fretter.
So, from that answer, if you are using an aid like this, you would play the C major scale on your fretted violin the same way you would on a non-fretted violin. The frets are just aids to help you with your finger placing. Now, if you have a high fretted violin, with higher frets like a guitar's frets, I would imagine you would play it like a guitar...with your finger behind the fret to hold the string against the fret.
As far as help with C major scales, check out a site called The String Club. (https://www.stringclub.com/) They offer 86 skill exercises and over 4000 songs using animated scrolling tabs showing you where to place your fingers, sheet music and tab notation for each exercise and song.
You will have to register to go through the entire exercise. You can register for free. A paid subscription gives you more benefits for $5 and $8 a month. If you register for free, they will offer you a 3 Month Complete Membership for a one time price of just $9.
Hope this information is helpful.
Sure @GregW Another one to look at is http://www.purelymusical.com/
They have violin and fiddle Score, tab & fingerboard display software to rent for $6 a month rental or $60 a year purchase. They are offering a 30% discount...code on the particular instrument page.