Translation:The girl wants a glass of orange juice.
In English, adjectives tend to precede nouns. E.g.: Orange juice, fried chicken, cold water. Flavors are considered adjectives, by the way, so they always come first. E.g.: Apple pie, chocolate cake, strawberry fields (forever), oops, this last one isn't really about food, but you get the idea.
The best way to type sentences correctly is to type exactly word for word the Spanish translation. Then, go back, and "edit" what you typed so that it makes sense in English. For example, first I typed the literal meaning: "The girls wants a glass of juice of orange." That is the literal meaning, but it doesn't make since in English. So now, before I submit the sentence, I go back and change it to: "The girl wants a glass of orange juice." Then I submit the sentence. I hope all this makes sense to you!
By the way, DonMaximusRomeo's comment is very helpful. Remember that most adjectives in Spanish come AFTER the noun that they describe, not before. So when you translate it to English, you have to move the adjectives. Hope this makes sense!
I think at some point though, it will be a good idea to let go of the two step process of translating. I like to visualise in my head what the sentence is about and then pretend I'm telling someone about it by saying the sentence out loud in Spanish. I don't read it off the screen though, but construct the sentence from the visual image I've created. This means that for typing out the translation to English, I'm translating an idea rather than a bunch of words so it should automatically make sense.