I wouldnt follow any email saying windows 10 is ready to install . The ony way ms will let you no its ready is through the icon on your desk top or through windows updates (both basically the same thing)
If you havnt got the message on the desk top check the icon as you may have some incomparability issues to deal with first .
The easiest way i found to install it was following this link
www.microsoft.com/en-us/software-download/windows10
All you need to do is choose which version os you have 32 or 64 bit and then choose what you want to do ie upgrade or make a usb pendrive/disk image . Choosing the upgrade option allows you to download and install . You can even choose to keep all data from your previous version of windows (when i say all data i mean all date and programs even book marks and installs of firefox browser etc) or clean install .
Ive used the above link to do to upgrades one on a laptop which went fine but i did have a couple of problems to sort out mainly the touch pad stopping and not working after boot and my desktop which was very straight forward .
Windows 10 is very fast and smooth and really gives the best of 2 op systems (win 7 and win 8 ) but you can modify it alot to the way you like things the first few hours can be a little confusing though but once you get your head around it its great .
Just remember over the years ms have made one good version one shite version of windows
Win xp= great
vista =crap
win7= fantastic
win 8= worthless piece of shite
Win 10= the best so far but im sure theres a few problems in it that need sorting
Just remember you need to do the upgrade first before doing a clean install or you will need to pay for a licence key and loose your free upgrade !!!!!!!!!!!