How i can upgrade my unity from 4.5.0 to 4.5.2?

When i check for an update in unity, there is the message, that unity is up to date.
My version is 4.5.0 but on the website is the version 4.5.2.

Should i uninstall the old version and download the new version or is there an upgrade?

when unity opens up you will be prompted to update unity, when you download the new version from the website you install and everything should be OK.