I need to make an arc inside a box how do I do that?

I also need to make a line dip in the middle downward how do I do that?

First click the "Insert" tab, select box and place it in the slide. I will assume that you know how to format the shape. Next click on the "Home" tab and in the drawing section click on the "arc" line and then place the line in your box. Make sure you format your line to be a different color than your background. Now, select your line and by manipulating the box size and the yellow diamonds on the line you can get the shape and size of the arch you need.

To put a dip in your line:
Go the view tab and check the gridlines box. This will show the gridlines on your slide. Click on the insert tab, click shape and then click on line. Insert 2 lines and place them on a grid line with a space between them. Next, insert a curve and draw it on the gridline, closing the gap between the 2 lines. If you magnify your slide getting the lines connected evenly will be much easier. Now select your curve line. Right click on the curve line and click on “edit points”. Move the cursor over the line, as close to the middle as possible, it will change to a crosshair. Now click and drag the crosshair to the position you would like your dip to be. This gives you a sharp dip in your line. Using the control key select all 3 of your lines. Click on arrange and then click on “group.” Now if you need to move your line, all 3 lines will move as one. If you want a curved dip, you can insert an “arc” line. Using the selection box around the arc and it’s end points, you can get it connected to the 2 lines, although it will take a lot of maneuvering to get it right where you need it. Again, group as above.