Many years ago I was active on RTTY using "real" mechanical monsters that were extremely noisy when being operated. My favourite monster was the Creed 7. (Maybe a Creed 7B?) I also used a Siemens T100, a smaller, and from what I remember a little less noisy than the Creed 7.
Nowadays of course computers are used instead. Also the schemes are much more advanced. When I was talked into taking up ham radio again FT8 (1, 2) was mentioned as a popular mode making it possible to reach far with modest equipment. A good technical description of FT-8 was printed in QEX, July/August 2020. pp. 3-13
The easiest way to get going given that you have a rig and a computer is to buy a SignaLink USB Sound Card. Strictly speaking this is probably not needed for a IC-7100, which is the rig I am using, as it has its own build-in USB Sound Card. But as the SignaLink was already bought and setup so I have continued to use it even with the IC-7100.
As of 2021-Mar-09 I have removed the SignaLink and is using the internal sound-card of the IC-7100. At least I gain one USB-cable less. I.e. the USB-cable to the SignaLink can be removed. The IC-7100 has an excellent set of controls for the levels and routing of the signals via the USB-port. So far it seems to work rather well! See the comment on my SW setup for more details.
Get a program
There are many pages written on getting started and using FT8 on the web. When you have a rig, an interface and a computer you only need to download or install a program that works with your OS. As I use Linux (Currently Mint 20) I decided to go for WSJT-X together with the logging program CQRLOG. They talk nicely with each other so all QSO's in WSJT-X are logged automagically in CQRLOG. The way I have set it up is to not use the CAT functionality in the CQRLOG. Instead all rig control is handled by WSJT-X. Here is a more complete description of how it is done.
Not only WSJT-X but also fldigi
There is another very popular program for running other modes. The fldigi uses the exactly the same setup and equipment so you only have to change the program. With fldigi you can run a lot of other mode. Some examples include RTTY, PSK31 & Hell and a lot of other not so often used modes! But unfortunately there doesn't seem to be so much activity using the other modes. Basically FT8 has become too / extremely popular.
FT8 dynamic range
When I started using FT8 I had problems with very strong neighbors. Before I really figured out how it was working I put together the following page on FT8 Dynamic range.