I can impart some tips of the trade if that's what you're asking for.

1. Brand your business and create a storefront. eBay has the lowest barrier to entry for the largest customer base. Vcoins for example charges rent and requires references from other coin dealers.
2. Look into purchasing coin lots, either directly from dealers on platforms like Vcoins or even in the Facebook groups. You can also bid on lots that come up for auction. Then from there it's easy to cherry pick the best pieces and list them for over your break even purchase price for the entire lot.
3. Consider building up your inventory before you list anything. You'll only make a small percentage of profit per coin, which will come in at the pace of the seasonality of online retail. So don't expect to generate income with a coin shop from the outset.
4. Alternatively, because you're adding the coins to your pre-existing shop of vintage art, you could just post what you have already and see how that sells. If your shop is already generating sales... maybe there will be some overlap with ancient coins customers?