Can I put the D'addario EJ32 Folk Nylon Strings on my Steel String Acoustic Guitar? If not, what can be my alternative? I haven't tried doing so and i'm scared since I might be wasting a pack of strings but I have seen people online do it already. Right now, I am using the D'addario Phosphor Bronze Light Gauge strings but I would still like a more mellow sound that the classical guitar would provide? What should I do?
Unless it has an adjustable truss-rod, I wouldn't.
The tension will be considerably less than steel strings & as a consequence the neck will start to drop backwards.
The action will probably already be too low the first day you put them on, & a fortnight later will probably be nothing but buzz.
Even with an adjustable truss-rod, you might find the action comes out too low, as the bridge & nut heights will have been cut for firmer, thinner strings.
As pointed out in comments - you may have difficulty in even getting them to attach. Nylon strings tend to tie on, steel have a ball-end.