Your logo can be resized with any image editing program such as Photoshop. You can also use an online image resizing tool such as http://www.lunapic.com/.
If you need your logo to be larger than 1000 pixels you will need to order a vector version of your logo.
Steps to resize your logo using Lunapic:
1) Click on the Browse button to upload your logo. To avoid loss of image quality, make sure the image you upload is larger (in both width and height) than the image you are resizing to.
2) Click on Edit > Crop Image if you wish to crop out any whitespace around your logo
3) Click on Edit > Scale Image and set the width or height so that your logo will fit within the new image size that you need
4) Click on Edit > Resize Canvas and set the width and/or height to be the image size that you need
5) Click on File > Save Image to save your re-sized logo