cumstom form to menú

Hi @Joanblanch,

I hope you are well today and thank you for your questions.

I tried to adapt the search engine to the menu of my site but I could not.
What do I have to do to adapt it?

You can achieve this by adding the below CSS code in the Custom CSS option of Ivory Search plugin settings on the path Ivory Search -> Settings -> Settings

.is-menu #searchform #s {
    background: #FFF;
}
.is-menu #searchform {
    margin-top: 6px;
    margin-left: 10px;
}

and to change the place holder that appears by default?

The search form and its placeholder text is displayed by the theme that you are using on your site so you can change it by editing theme searchform.php file in the child theme as described in the following page.

How to create a custom search form in WordPress

Alternatively, you can change the text by translating your theme or using any of the below plugins to change it.

Say what?

Real-Time Find and Replace

Best regards,
Ivory Search Support