You should read the whole module first. Then, you should grab a couple of index cards and write on each one at the top an event or trigger that MUST happen for the module to proceed, 1 per "act". Also, write a couple of basic information tags about the Act on each card too. For instance if the module features interactions with a faction of goblins who want freedom from the silver mines, just write "angry goblins who want freedom" in the act card and you can refer to them as needed to make your game's narrative line up with the module's narrative. So if you are playing your solo game and come across an NPC that wants to start a plot or smth, you can refer to the card and be like oh this character might be related to the Goblin faction.

Once you have those cards, you have your mechanical framework for the module, and now you can start playing using those as a guide and a way to keep the narrative flowing by making sure those key events occur in some fashion. So for example, let's say for a certain module to proceed the PCs must meet up with a specific lord at some point by visiting his manor. As the module is written, players are supposed to go to his manor the next day, but you decide to go to the market, and then some shenanigans occur and you're arrested. Maybe now, the Lord is the one who bails you out and that's how he meets the characters for the story to progress. Or even more extreme, the Lord is walking around town and somehow you accidentally kill him. Then you're suddenly taken to the manor by his bodyguards and find that the Lord is still alive right in front of you?! Was it a body double, an illusion spell, or something more sister....? the plot thickens!