Without knowing your operating system it's hard to provide detailed instructions on how to do this, but the first thing to say is that you only really need to backup your data files. There's no point in copying the operating system or any installed programs assuming that you have the software on discs or they came ready installed on the laptop. I am assuming that the external drives have a USB connection and that your laptop can accept USB. These days just plugging in the USB connector and making sure the external drive is powered up is all you need to do to get your laptop to recognise the external device (I suggest only plugging in one to start with). Then if you know where all your data files are located, navigate there and having selected the top most directory containing the relevant data (possibly something like My Documents in Windows), right click copy or the equivalent if you have Mac, then navigate back to the external device and paste the data to it. The process will replicate your file structure on the external device, making it easier to find the backed up files should you need to. You will probably find that one external drive will hold all your data, but if not you may have to split the data between the two external drives, for instance your family history stuff on one drive and all your correspondence and manuscript of your book on the other. You should also copy over any lists of logins and passwords which are stored locally on the laptop. These will be stored within your browser's files, so if you look in the help files for your browser it should tell you how to do this. Depending on how your email is configured, you might also want to back up all your email addresses - again check with your email provider for details. I would also backup your list of internet bookmarks (called Favorites or Internet shortcuts in Internet Explorer and Microsoft Edge) - again found in your browser's settings.
