Service panel has neutral and ground bar. Do I connect both neutral and ground leads to the ground bar? 4 wire connection to 240 volts.

Define "Service panel" please. Is it SPA related?

Panels fed from the main panel require that their grounds and neutrals remain separate. Neutral to ground bond screws are removed. They require a 4 wire service and a ground rod if in an detached structure.

I've asked that your post be moved.

Good morning. I'll just take a moment and warn you the working in the "Service" panel can be deadly. If you are not absolutely sure how to do things correctly and safely then please call a licensed electrician.
In truth before we even get started helping you, we need to know whether you are putting the subpanel in a separate building or in the same building as the Main Service Panel.

To begin with since you are adding a circuit to the "Service" panel, you must get a permit. (FYI - The Service Panel is the panel that accepts the feed from the utility company and distributes it within residence.)

Sub panels are are fed from the "Service" panel.

Within the Service or Main panel, both Neutral and Ground are "Bonded" together. However, for any subpanel, Neutral must be isolated from ground.

You also have to "size" the amperage needed for the secondary panel. This includes determining the necessary load requirements that the panel will feed.

You also need to plan the type and size of the sub panel, the size and insulation of the subpanel 4 wire feeder, a main cut-off switch (depending on the type of panel used) and much more.