add a link to some text which will open up an image

I’m hoping someone can help me with my dilema. I’ve searched but cannot find any help yet.

First of all, i cannot show a link to the site yet as it’s only on my computer. My client has not yet paid for any hosting.

My client would like to be able to add a link to some text which will open up an image. This can easily be done with a thumbnail linking to it’s image, but not with text.

Now where as i know how to do this by inserting an image using Add Media, then copying the Link URL location, then adding this to the text using the Insert/Edit Link in the Visual Editor, this is going to be a bit confusing and long winded for my client.

Is there an easier way of completing this task (say for the less intelligent people)?

Step 4 (of this page https://en.support.wordpress.com/images/) shows the Media section after upload of an image, which shows in bullet 7 the four options (Thumbnail, Medium, Large, or Full Size).

If you try this with a PDF file you obviously don’t get these options. Then when you click the Insert Into Post button, the ‘Title Text’ is shown in the post (removing the original text, but that’s not a problem), but this now includes a link to the file, which is what i am after, just with an image.

This is not the same as with an image. With an image, you have to choose either Thumbnail, Medium, Large, or Full Size. Why is there not a line here for Text [say using the Title Text] (which would show text linking to the image)!

Is there any code i can add to functions.php to add something like this to the media upload area?

Any help would be much appreciated.
Ian