Formerly the app has only features for creating size charts. But now you can use it for adding any pop-ups to the product pages.
Because of this, the docs may have some outdated info. Feel free to contact the support if you have any questions.

Install the app

How to change size chart link text and style?

Change `Size chart` link text

In order to change the size chart link text go to the App > Settings and in the field Size chart link text under the Main settings tab, write any text you want

Change the style of a link to a button

Also, you can change appearance from link style to a button using the switch Show size chart link as and you can add your custom CSS styles and even use inline HTML styles for the link

For example, you can change the style of a size chart link as at the image, by adding this snippet in the Custom inline style field:

box-shadow: 0px 1px 0px 0px #f0f7fa;
background:linear-gradient(to bottom, #33bdef 5%, #019ad2 100%); 
background-color:#33bdef; 
border-radius:6px; 
border:1px solid #057fd0; 
display:inline-block; 
cursor:pointer; 
color:#ffffff; 
font-family:Arial; 
font-size:15px; 
font-weight:bold; 
padding:6px 24px; 
text-decoration:none; 
text-shadow:0px -1px 0px #5b6178;

Or, even better, you can add your own styles to reference in the CSS file of your theme, and list the style classes in the Custom CSS classes field. For example, add this code snippet to custom CSS of your theme:

.mySizeChartLink { 
    box-shadow: 0px 1px 0px 0px #f0f7fa; 
    background:linear-gradient(to bottom, #33bdef 5%, #019ad2 100%); 
    background-color:#33bdef; 
    border-radius:6px; 
    border:1px solid #057fd0; 
    display:inline-block; 
    cursor:pointer; 
    color:#ffffff; 
    font-family:Arial; 
    font-size:12px; 
    font-weight:bold; 
    padding:3px 10px; 
    text-decoration:none; 
    text-shadow:0px -1px 0px #5b6178; 
} 

.mySizeChartLink:hover { 
    background:linear-gradient(to bottom, #019ad2 5%, #33bdef 100%); 
    background-color:#019ad2;
    color:#ffffff;
} 

.mySizeChartLink:active { 
    position:relative; 
    top:1px; 
    color:#ffffff;
}