Are you trying to resize the image or crop it, or both?
If you have a specific size you want it to be and the original images differ in width and height you would be best placed to go trough Image>Image Size... (Ctrl+Alt+I) first, then specify the correct proportion, so in this case get you 700px width then ok that then crop the image after that to the correct height.
Hope that makes sense?
I am trying to do both, crop and resize. So if I go to image, image size and change the width and height to what I need it to be, then crop it, do I need to change it in the fixed ratio section (where is says width and height in the main bar at the top of the main screen)?
Thank you so much for your reply
Ok, say you were to convert an image that was 1000x800 to 700x525 you would go to image size change the width ONLY to 700 then ok that.
Then go to your crop tool and add in your fixed ratio of 700x525 then hit return twice and it will crop the image to that specific size.
If you want to do this an a fairly small number of images it may be worth setting up an action (Recording Actions | Learn Photoshop CC | Adobe TV) to speed things up, but if you are performing this on a lot of images you may want to look at batch processing (Batch Processing | Understanding Adobe Photoshop CS6 | Adobe TV). these two options only work if you are working on images with the same proportions.
I hope this all helps. Thanks.
That is very helpful, thank you so much
Keep in mind you can also use 'Canvas Size' (Ctrl+Alt+C) instead of 'Image Size' to change the canvas to the exact size Width and Height in whatever units you choose. This is separate from your image's width and height. Then you can transform (Ctrl+T) the layer of the image to fit within that canvas size anyway you like. Remember to double click your layer if it is a background layer. Hold down Shift if transforming to maintain image ratio. Expand it beyond canvas to get the cropped look you want.
I sometimes find this faster/more intuitive then using the crop tool and the ratio boxes at top when resizing a single image. Less math more visual manipulation.
If you're going to crop and resize, then I would do the cropping first. Just set up the proper aspect ratio in the crop tool (7 x 5.25), and crop it to whatever composition you like. Then set the image size.