Hehe, if you say "I downloaded many things online but couldn't enter DOS after burning to disc", it means your burning method is incorrect.
If you downloaded an iso file, you should choose the "burn image" mode for burning when burning.
If you downloaded an img file, you need to import it into the disc (or make it into an iso file) and then burn it.
If what I said you don't understand, it means you need to lurk more and study up. You might as well search online for "very detailed boot disc making tutorials" to learn.