I cant login to edit my site

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Hi, firstly let me explain i am a complete novice.
I was having snags with googlebot and other robots, so i did some research on the forum and other places and added /robots.txt to my URL – obviously in the wrong place!
now when I try to log onto my site https://www.dg-music.co.uk/wp-admin i get the following in the address bar https://www.dg-music.co.uk/robots.txt/wp-admin.

My site is now not loading correctly and I cant get in to log in and undo my huge mistake.

any help would be greatly appreciated.