I'll try to answer in context below:
Margins all round = 1 inch
At the top of your document, hit alt then p and the first item should be margins. Hit enter and tab through your choices. 1 inch should be one of the options, if not, select customize and make them all 1 inch.
Single line spacing
I'm not 100% sure on this one, but I believe if you select the entire document and hit control+1 it will make it single line spacing. The problem I have is that Word wants to default to some spacing after paragraphs. If you again hit alt then p and then tab until you hear spacing before and spacing after, you can check those.
Font size 12
Font in Times New Roman
Hit control+a to select the entire document, then hit the application key or shift+f10 and arrow up or down to font and hit enter.
You will be in a list and if you hit the letter t and then arrow down you should find Times New Roman, then tab to style, which should be regular, tab once more to size and either enter 12, or arrow down to 12 and hit enter.
I hope that helps,