Navigate to the reports Object/Tab and use the Search button to find the report you would like.  If you know where the report is you can look in its folder, or if you used it recently, you can use the Recent Reports tab.  Click on the report to take you to the Run Report WIndow.  In this case we are going to use the All Users - Demo report.  Then click customize.

This report is a mess.   I don't want Username listed first, I want last name, then first name, then Username and then email address.  

To change the order the columns appear, we will just grab the column with our mouse and drop it where we want it.  As we move the column, we see that a highlight appears where this new column is going and the box turns from a red X to a Green check.  This means that I am allowed to move this field header here.  In this example, I am moving Username to the other side of the First Name.  When the column is where I want it, I just release the mouse and the report will adjust accordingly

You can also click on the column header to sort the report by one column or another.

I am not particularly interested in the User's Profile, so I am going to remove this field.  This is exactly like moving a column header as instructed above, but this time, I am going to grab it and place it back in the available fields menu.  Basically, you are just grabbing it, and dragging it off your report.

It does not matter where it appears you are putting the field... HOC will put it in the right folder... this is just to drag it out of your report.

Adding a field is just as intuitive.  First, we need to find the field we want to add to the report.  The simplest and fastest approach is to search for that field in the Field Menu on the far left side4.  I am looking for Gender, so in the search box, with ALL selected, I type in Gen

Notice the fields appearing below.  I have now found all fields that have gen in the field header.

The folder name tells you the Object that the item comes from, and the list below tells you the name of the field, and what kind of field it is.  In this case, because they both have the letter a next to them, they are both alpha or alphanumeric fields.  I am looking for a Contact's gender in the Contact Object, and not the Genders Served in the Organization Object.

A new column will appear with the field you added.  Remember, this is just a sample of the data you are looking for.  To see all the records, hit the Run Report button at the top of the screen, which will take you back to the Run Report Window.

If you wanted to delete all the fields in a given report and start over from scratch, you can use the Remove All Columns link.

We don't recommend SAVING the report with the changes (as others in your organization may want the original template as it was), so use SAVE AS and save the report to a different folder.