Go to the website providing you with the HTML or JavaScript code
Highlight and select the HTML or JavaScript code
Right click on the code and go to Copy
Login to your wordpress blog by going to http://domain.com/wp-admin/
If you want to place this code on a Post or Page follow the directions in order. If you want to insert HTML/JavaScript code on your sidebar go to step 12
Click Manage, Post/Page, click on the title of the Post/Page you want to insert HTML/JavaScript code to.
Click HTML at the top right of the Post/Page box
Click to place the cursor where you want the code to appear
Right click and go to Paste, you should now see your HTML/JavaScript code you copied
Click on Visual at the top right of the Post/Page box.
Click Save/Publish, you are done!
Click on Design, Widgets (Only if you want to add this code to your sidebar)
If you widgets are not already on your sidebar, add them in the order you want them to appear
Now add a Text widget, this is where we will place your HTML/JavaScript code
Click on Edit on the the Text Widget, which will open a window with 2 boxes top/bottom
Leave the top box blank, right click in the bottom box of the Text widget and go to Paste
You should now see you code here, click change on the bottom left, this window will shrink back up
Click on Save Changes at the bottom of your sidebar widget list