[Wordpress issuses] chuwey on "change blog address to my other (empty) blog address"

Dear All, I am not sure if this question already asked before.
But please help my situation.

I currently blog on chuwey.wordpress.com and want to change the blod address to ladymongrel.wordpress.com

But I previously already made ladymongrel.wordpress.com and write some project there. The project did not work well. so its stop.

Now i decide to replace chuwey.wordpress.com with ladymongrel.wordpress.com, discard the content of ladymongrel.wordpress.com

Could anyone suggest me the best and correct way to do it.
I am not sure if i had to delete the ladymongrel.wordpress.com first since it said i will can not use it again.

Thank you very much!

The blog I need help with is chuwey.wordpress.com.

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