Community Store is a developer level ConcreteCMS extension providing eCommerce for ConcreteCMS v5.7+. It is not developed or supported to the level necessary for distribution through the ConcreteCMS marketplace.
You can find it on GitHub at https://github.com/concrete5-community-store/community_storeand installation on a site is by necessity a manual process involving downloads, unzipping, renaming directories, FTP into a site and finally installation through the dashboard.
All of that is greatly simplified using the full version of Package Magic. Having installed Package Magic Starter and Package Magic from the marketplace, go to Dashboard > Extend > Upload Package.
Choose From URL as the package source. The next field is Enter URL or filepath to load archive from. Here you can paste in the current latest URL for the Community Store zip, available from https://github.com/concrete5-community-store/community_store/releases. At the time of writing, this will be v2.0.5 and the URL will be https://github.com/concrete5-community-store/community_store/releases/download/v2.0.5/community_store.zip. On most browsers, you can hover over the download zip link on the community store page and right click then select Copy link address.
The problem with zips from GitHub is that sometimes the zip does not follow the ConcreteCMS convention for packages. To resolve this automatically, open the Advanced Options and check Fix paths in archive from package handle.
With the zip being automatically generated from GitHub, it usually contains some unwanted but harmless files such as hidden .dot files. You can see them now by clicking the Check Package button, next to right at the bottom. Rather than mess about removing these, as long as you are happy they are harmless, open the Relaxed Validation section and check Ignore .dot files and directories.
Now when you click the Check Package button you should see a report confirming No problems detected in archive community_store. Clicking the rightmost button Install/Update Package will now unpack the zip file in your site /packages/ folder ready for Community Store to be installed.
Now you can simply use Dashboard > Extend > Install to complete the package installation.
There are, however, a few other things you could do first. Under Dashboard > Extend > Package Tools you could use package magic tools to expand short tags. Under Dashboard > Extend > Download Package you could then create a new package zip with short tags expanded and without any hidden dot files, ready for a clean installation from your development system next time you need to deploy Community Store.