We encourage you to check if the download was not modified by some malicious person or by an error while downloading. As a simple check, you can generate the SHA1-sum of the downloaded file and compare it with the one we provide here. Here you can find information how to generate such a sum and check your downloaded files.
To even further enhance the security, verify the downloaded file with a GPG (GNU Privacy Guard) signature that will ensure that the file was not modified and was actually created by the Manjaro developers. Here you can find information how to use it.
When you are ready, follow ‘First steps’. We also encourage you to read our MANUAL.