Updating data within a Custom Post Type on the users screen not admin

I want to use custom post types instead of database tables.

I've created the CPT and can post data to it from the WordPress admin - however, I would like users to be able to post to it too, and also edit and update their own entries (this will be a fitness tracker type site).

I can read data back from the CPT and display it, but when looking for any info on updating data in the CPT, all I find are references on how to update the CPT itself, not data within it.

This is my code for reading from the CPTs:

if ($query->have_posts()) {
   while ($query->have_posts()) {
        global $post;
        $query->the_post();
        $id = get_the_ID();
        echo $id;
        $post_meta = get_post_meta($id);
        $measure = $post_meta['measure_description'][0];
        $record = $post_meta['unit_type'][0];
        $latestres = $post_meta['latest_result'][0];
        $datet = $post_meta['result_date'][0];
        $postauthor = get_the_author();

//show data onscreen here

        }
    }

Can anyone point me to a reference on how to post data to a CPT and how to update data in an existing CPT record?

Thank you,

Mark