When you enroll in Medical coverage and elect to open an HSA, you do not have to contribute any money at that time. You can, however, change that contribution time at any point.
In 2024, the HSA limit (the maximum amount you can contribute) is $4,150 for employee-only coverage and $8,300 for family coverage. If you are age 55 or older in 2024, you can contribute an additional $1,000 to your HSA.