I agree with the post above. I teach at the college level, and I wish something like eNotes had been available to me when I was a student! It's a resource I can (and do) heartily recommend to my own students and to other young people I know. Even people who are no longer young (myself included!) can very much profit from eNotes. I have learned quite a bit while writing for eNotes.
Its not possible here to give you summary of each line. Post#2 and 3 have given you good suggestion. Yet you may not be able to subscribe right now. By the time you talk to your parents and become a subscriber have the following.
In the first stanza or tercet, the poet urges his very ill father to fight his illness. It is expressing a hope rather than an actual command because his father never heard the poem. Dylan Thomas declares that even in old age the old should violently resist their death. The poet urges his father to angrily hold on to his life. In the second stanza, Thomas states that wise men may know that death is natural but they too resist death violently. They hold on because they realize they have not made a sufficient impact on society with their wisdom.
In the third stanza, Thomas states that honest men don’t accept their deaths because they want to live on to give better example to others. In the fourth stanza, Thomas states that men who lived mad and wild lives don’t give in at the end. Thomas describes them as men who enjoy the sunny side of life so long they miss it and cry for it as they die. In the fifth stanza, Thomas states that men who lived serious lives are angry at death because they realize that they could have lived energetic and passionate lives instead. In the final stanza, Thomas addresses his father in his mind. He wishes that his father would give him his blessing but also curse him out of jealousy for continuing to live.