The phrase "to follow the timeline" means to understand the sequence of events or actions as they happened in the correct order. It refers to tracing or tracking the chronological order of events. Full definition
Add the broth and grains (if cooking grains in soup, add another 2 cups of water to soup and follow the timelines outlined initially). (immigrantstable.com)
The letter encouraged states to «continue to move forward» on draft plans and follow the timeline for final submission. (understandingessa.org)
Following timelines generally isn't for us when traveling, so we were a little skeptical before sailing. (greatbigglobe.com)