Expanding a bit the reply by @TechnoBear ; You will of course need a domain name and it makes things easier if you get the domain name from the same people who are doing the hosting as they will set every thing up.
You are not restricted to get the domain name from the company that are doing the hosting but then you will have another step. The hosts should provide you with some DNS settings which could be something like:
You then need to put these into the relevant boxes in your control panel provided by the company you brought your domain name from; on their website. Depending who you brought the domain name from they might be helpful and do it for you.
But whatever path you take if you have a problem come back and ask a question.
You say " developing my 1st website " Is this a CMS; if so you will probably need to setup the database etc. as well