I have one day a week for maybe 45min at a gym...

For context: there was a time several years ago where I went 3 days a week doing a lifting routine. I think my heaviest dead lift was maybe 140lbs.

Two kids later, hernia surgery, and a change in position at work that has me sitting way more (used to do solo IT work for multiple buildings, now I have a team and do mostly back end admin work), and I've lost all my gains and put on about 20lbs.

Kids are more manageable now solo, and I'm looking to hit the gym every Monday I can.

How do I maximize this time?

Thanks in advance comrades!