To install Adobe InCopy CC2018 you will need a Creative Cloud account (with a paid subscription for InCopy) as well as the "Creative Cloud Desktop App". For more information about Creative Cloud licensing please see the information here. The "Creative Cloud Desktop App" can be downloaded here.
1. Once the "Creative Cloud Desktop App" is installed click on the Apps option.
2. Then click the "Install" button found to the right of InCopy CC.
Note that if you have an earlier version of InCopy installed the download option will be called "Update" rather than "Install". Installing CC2018 will uninstall any earlier versions. To avoid this please see the information found here.
If the download option is labelled "Try" it is because you are not logged in with an Adobe account with an active subscription for InCopy. You can still install InCopy as a free trial for 7 days, howevever after this time has expired you will need a subscription.