Confusion with self-hosting & moving from WordPress.com

Hello,
MY blog is on wordpress.com at https://vohnmcg.com and I am moving to self-hosting. My host has installed WordPress on my cloud with them & has migrated my blog to my new domain name. However I have some problems…
– I can’t get the new test site to load on my Mac (Safari web browser), only my PC
– The host has said it can only migrate my blog posts – they have not migrated any photos – is this correct and I have to re-load all my photos?
– The host has not migrated any comments – is this correct and I have to loose all my existing comments?
– I can’t actually work out how to use Wordress (i.e. create new posts/ change theme/ etc) – is this something I should be doing via my host’s cloud, or should I be installing WordPress on my laptop and logging into it directly (not via host’s cloud)?

I am very confused and would appreciate any help and guidance anyone can give me to get my new site up and running.
Thanks so much,
Vohn