The style of this arched window

You'll want to use glazing compound, which comes in both oil-based, and latex, and can be found in both cans or tubes.

Once you have the glass removed, and the frame cleaned up.

• Run a bead of glazing compound around the frame (where the glass will sit).
• Set the glass in the compound giving it a little wiggle to work out any air bubbles, and to make sure the glass is set in properly (don't worry about a little excess oozing out, you can trim it off later when it cures).
• Using a putty knife push in glazing points every 6-8 in.

• Install the interior trim, and wait for the glazing compound to cure.

• Once the compound has cured enough (24-72 hours), using a utility knife carefully trim off any compound that has oozed out.

• If you are not using interior trim, you will want to apply a bead of glazing compound to the interior side of the frame, and use a putty knife to smooth it to a nice finish.

• After 7-10 days you can paint the glazing compound to match the frame.

It's a window latch and keeper. Unscrew a good one, head over the your local hardware store, and see if they have a match in stock. Pay close attention to the distance between the screw holes and the how tight the two parts are pulled together. They come in a lot of styles, e.g. this would work if the keeper was on a horizontal instead of on a vertical surface:

You can also look online, and worst case scenario, you'll have to go to the window manufacturer to get the replacement parts.