Before you link a programme to the model, read it: what drives what, which activities can slip and which cannot, and the open ends that make a finish date look safer than it is.
A programme looks like bars on dates. What makes it a plan is the logic: the links that say this cannot start until that has finished. Read the logic first and the bars start to mean something; skip it and you will link a 4D model to dates nobody can rely on.
Each activity has a duration. Links connect activities: most are finish-to-start (FS: B starts when A finishes); some are start-to-start (SS) or finish-to-finish (FF), sometimes with a lag (a wait, such as concrete curing). Working forwards through the links gives the earliest dates; working backwards from the finish gives the latest. The gap between the two is the activity's total float.
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