Jesus stays with the disciples 40 days, teaching them about the Kingdom. They will not fully restore it, but bear witness to it and Him to the ends of the earth, by the Spirit's power. The rest of the book of Acts describes this work of the apostles done through the Spirit. Jesus ascends to heaven to rule His kingdom and subdue His enemies from there (Ps 110).
You have the power of the Spirit from Jesus to bear witness to Him where you are. Are you doing so?
The apostles are now joined by Jesus' family, and 100 or so others. Peter leads them in replacing Judas. The first act of the Spirit in Peter's doing so is to lead him to quote the Word, showing from Psalms what Judas was. It was important to have 12 apostles, not 11. They realize they are the new Israel.
While the acts of the apostles in this book are not always commands for what we should be doing today, in this case we can ask: are we able to apply the Word to events concerning us and our witness to Christ, so as to guide us to more effective bearing witness?