Ahh... Betamax. Those were the days!
You`ll need an analogue capture card, if you don`t already have one - look either on the PCs front or back for video input sockets (it may be a round yellow plug hole) and audio in (red and black) - if not you`ll have to either fit one (very cheap now) or get an external one that plugs into a USB port (still cheap) - there are quite a few on the market.
See what outputs your Betamax has; it`ll hopefully at least have a similar yellow socket as an output, and hopefully one or 2 audio outs. It`s been a few decades since I`ve seen a Beta player, but I doubt it`ll have a Scart or S Video outputs.
If you have to buy a card / USB device, don`t worry about paying more for one with software unless you are not running XP.
Let us know the connections and your Op System and we`ll take it from there.