Board Thread:Support Requests - Designing Your Wiki/@comment-37602118-20200216062312/@comment-9605025-20200216082945

It looks like your wiki does not have the JS review process enabled yet. You will have to send to staff to have it enabled. Once it is enabled, you can install ChatHacks by following the installation instructions. Keep in mind that even after the JS review process is enabled for your wiki, each revision needs to be approved before it "goes live". Assuming there are no issues with the submitted revision, it will typically take no more than a few US business days for it to receive approval.

As for the custom welcome message, you can edit "MediaWiki:Chat-welcome-message" on your wiki.