Well the first question is in what form is the block of text? Typically, if it is on a web page then you can select it, copy it, paste it into Google translate
. Usually it will auto-detect the source language and select English as the language to translate into. If it doesn't you can select them manually. You can also select and copy the URL of the web page and paste that into Google translate but it doesn't always work. If the block of text is in a word document or a Notepad file the above method will also work.
PDF files are a bit more difficult. I find that if you simply select, copy and paste into Google translate text from a pdf file it appears as total garbage. Personally I use an OCR program called IRIS to transform the pdf file into a Word document and then copy and paste that into Google translate. There are online web sites that will do this for free.
Google translate is a lot better than it used to be but it is still far from perfect. If you select short sections of text and paste them into Google translate it gives you the opportunity to select alternative translations if the first attempt doesn't make sense.