A new license can replace an older license that is expiring and/or upgrade the capacity limit.
If you install a new license on or after its start date, it is activated in place of the current license, which is forcefully expired if it is still active.
You can install the new license before its start date. The current license remains active unless it has reached its own expiration date. The new license is activated on its start date. The older license is forcefully expired at the same time if it is still active.
The procedure for installing a replacement license is the same as installing a first time license.