As i see the area is in CMS > Website Manager <https://i.postimg.cc/8cRqT1SQ/Screenshot-2022-05-09-at-11-51-49-Admin-Benefits-Settings.png>. On Website Manager Page click on Builder Button <https://i.postimg.cc/XqLQ2XWJ/Screenshot-2022-05-09-at-11-17-16-Admin-Benefits-Settings.png> which one is along side with home. Then You can see the builder page of home page. On this Builder page this search Section is a part of Top Banner Area.
Click on the Input box of search area. After click you can see on left panel there are option to change style of this input.<https://i.postimg.cc/brV1Dn8Q/Screenshot-2022-05-09-at-11-17-48-Page-Builder.png,
And Also From where i can find credentials for portal.inteliquent.com API ?