Newbie asking about text boxes

I’m trying to develop a text box within my blog, similar to how I’m entering my information right now. I want to request email, phone, and other contact information for an online application form.

Can somehow show me how to code this in or add? It seemed like it was a widget thing, but then I found that widgets just pertain to sidebars.

Any help appreciated! At a loss and getting kinda frustrated with what I thought was a very flexible platform!