Which version of Lightroom did you buy last year?
I assume your new download is 5.6 so you'll need to have a serial number for 5.x.
If your serial number was for an earlier version you'll need to upgrade or download a new copy of the version to which you do have a licence.
If your licence is for 5.x then it's possible you've been sent a link to the CC version rather than the standalone. If this is the case you'll need to un-install this a download from one of the following links instead.
The version i bought is the 5 as I red on the mail of purchasing. May be this is the second case becaouse to download this i had to install the CC, thank you and I will try now
Thank you so much!!! Resolved with the standalone version
Good, glad to help, thanks for updating me.