How to know its time to add weights to hammer strength squat rack

I'm kinda new to being consistent at gym and have been working on just building consistency. my goal is to have more energy, mobility and strength/build muscle.

I've been doing the hammer strength squat rack when at the gym and while I get tired, I don't necessarily get sore. however when i do squats at home with dumb bells I do get a bit of soreness.

in the past I've had lower back pain issues so I definitely don't want to hurt myself but how would I knle when I should start adding weights to the rack?