1992 Chrysler Le Baron Smoke from under the hood

This car wasn't run for a couple years. Last year my ex fixed it up for our teenagers. Since then it has run about 800 miles. Last month I had a brake line replaced and the rear track bar. Now the check gages light comes on and the temp gage moves quickly to H. We live in a mountainous area and this seems to be avoided when dropped to 2nd going up hill. Last night, however, it didn't drop and by the time I got to a place to pull over, there was smoke coming from under the hood. I turned it off and let it sit for about 30 minutes. I had no problem after that. Then this morning it was doing the same thing. What do I need to put in and where do I put it?