When you read some instructions and then report them to another person, use the phrase "It says to ___." For example:
It says to add the onions and celery and simmer for five minutes.
For warnings, say "It says not to ___":
It says not to touch the connectors.
You can also specify where the instructions came from:
The sign says not to go in there.
It might seem strange to use "says" with written instructions since the instructions don't actually speak. But English doesn't have a separate verb to describe information that's written down, so we use "says".