Those are not stupid questions, so don't worry.

To add compost (or fertilizer,for that matter) to a mulched bed, you pull the chips away from the plant, either with a hoe or cultivator or with your hands (I recommend wearing gloves), add the compost, then push the mulch back into place.

If you're putting in marigolds or other annuals, the dirt that's there will almost certainly work. Depending on the state of the soil, you could loosen the soil around where the marigold is going in, so the roots can grow a bit easier. Digging a hole for a plant and then filling around the plant with different soil rarely, if ever, turns out well, as the water will drain at different rates, usually to the detriment of the plant.

I recommend getting a good all-around gardening book; Reader's Digest used to have a good one, as did Better Homes & Garden. Check out your library to see what they have that would be helpful. I've been gardening for many years and I still refer to my books when I get stumped. The people on Gardenweb are great and will help with any questions,but sometimes there's a wait for a response, and a book might help fill the time.

Enjoy your garden!

The soil you have there will be fine if some organic matter is added to it and that should be in the 6 to 8 percent range.
Where in the United States you are would be of tremendous help even though lisanti did a good job of answering your questions.
Contact yourlocal office of your state universities Cooperative Extension Service about having a good, reliable soil test done so you know your soils pH and major nutrient levels and then dig in with these simple soil tests
1) Soil test for organic matter. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drainsâ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.
to get more information about that soil.
There may well be people will post here that you do not need to do any of these tests and they are right you do not need to. But knowledge is always better than ignorance.