SharePoint passing value of text box on click to update list column

I am new to SharePoint and have a task to complete. I have a text box on one SP page. Upon click of the submit button, I need the numerical value/input to be sent to a column in a list and update it. Seems like something so simple, but I can't figure out the coding to pass the value to the list column. For the button, I have the following code so far:

<input id="userInput" type="textbox" name="overallgrading"><input type="button" id="overallgrading" value="Submit" />

Where overallgrading is the name of the column in the list that I need to write to. I think there needs to be some sort of update function to save/pass the value, as there is a preset value of 0 in the column. I appreciate any help I can get!