Turn your laptop on for these. Payments and initial setup are best made on a PC proper. Buy the domain name and hosting, then install WordPress. If this sentence does not make sense to you, go to WordPress and get a free domain name through them, it will save you a lot of hassle.
Once WordPress, which is your blogging platform, is done, go into settings and under writing enable remote publishing. Otherwise your phone will not be able to log onto your blog to post your stuff. Also install the basic WP plugins every blog should have, starting with Firewall.
Choose your theme. Choose the colours, fonts, headers, favicons. If this is the first time, it may take a week until you become quite content with its looks. Luckily, you can always go back and change it later.
Last step. Add the blog to the WordPress app on your mobile. All you need to enter is the domain name, username and password. If it does not work, you forgot to enable remote publishing.