I'm a novice at instruction, but here goes:
We need to know if your scanner has OCR. Can't really help with this, but if you go into the "help" menu when you start your scanner, maybe there's a search facility and you can search for "OCR" and find out. But let's assume you don't have it.
Click on this link to download this simple program. Click where it says "Download Now" - if you see a small bar across the top of the screen saying "...download prevented....." , left click on it and then click where it says "download file" Don't worry, it's safe. (I've just done it, and scanned for virus etc.)
Run the download file (you can save it to a location on your PC if you like but you don't need to); install the program; (I'm hoping this is detailed enough?)
You will see a new icon on your desktop "Free OCR" - open the program. Read the instructions in the right hand panel, then clear them by clicking the little red "x" between the two panels.
Place the Spanish letter on your scanner. Click the "scan" button at top left in FreeOCR. An image of the letter should appear in the left hand panel. Now click on the "OCR" button. A text renderring of the letter should appear in the right hand panel.
You can save this text directly to Word using the Word logo between the two panels, or if you don't have Word or want to save it to a different text editor, click the save button (below the red x) and then choose where and how you want to save it on your PC.
Alternatively, if you just want to translate it straight away without saving it, place your mouse pointer in the right panel, right click on it and choose "select all". The text should now all be highlighted in blue. Right click again, and select "copy".
Now click this link to open Google translate, right click in the panel on the left and select "paste". if Google translate doesn't automatically recognise it as Spanish, you can change the "from" and "to" languages yourself, and your translation should now appear on the right.
Check the scanned text is correct, as some letters may have been wrongly read (an "e" may have been read as a "c" for example) but otherwise, that should be job done.
Let me know if this helps?