Come now, let us reason together,
says the Lord:
though your sins are like scarlet,
they shall be as white as snow;
though they are red like crimson,
they shall become like wool.
If you are willing and obedient,
you shall eat the good of the land;
but if you refuse and rebel,
you shall be devoured by the sword;
for the mouth of the Lord has spoken.
Divine guidance can be expressed in many ways, according to how you are most likely to receive it. Certainly, dreams can be a powerful means of expression. That's not to say that all dreams have spiritual significance, of course. We can rely on our inner discernment to make us aware of the dreams that can be useful, as you are in this case.
As for Isaiah 1:18-20, it is a part of the prophet's lament that Judah—the Southern Kingdom centered in Jerusalem—is disregarding the guidance of the Lord, and the sacred covenants agreed to by their ancestors. Speaking for the Lord, he is making the people aware of the universal spiritual Truth that choices have consequences. If they choose to return to obedience to the spiritual Law that has guided them throughout their history, the painful consequences of their disobedience will be dissolved, no matter how grievous their negative choices may have been. If, instead, they choose to continue refusing to honor divine law, the consequences will be severe; their nation will be "devoured by the sword."
How this passage relates to your life is something that can only be recognized by you, in your quiet times of prayer and meditation. Perhaps you are regretting choices you've made in the past, and the guidance is that you can release that sense of regret and allow the Lord of your being to dissolve all negative energies.