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".