Setup
The Setup process for Cumulus is briefly mentioned in the 'readme.txt' and covered in detail in the help files. Once Cumulus is installed: Click Start, Programs, Cumulus and select the Help. Expand the Introduction section and begin reading at "Getting Started" until you have got everything working.
In addition to the help, there is a handy installation guide here
Configuration: Settings
Configuration settings information for your particular Cumulus version/build is in the Cumulus Help. Most of these settings are fully explained in the help for each screen in the configuration menu. But there are two panels on the 'Station' screen that frequently lead to questions in the support forum - location and units - explained further below.
Some advanced settings can not be set using screens in Configuration menu. The information in cumulus.ini describes all configuration settings for the latest Cumulus release, whether set via screens or directly in that file. (It may mention some additions established in beta builds, other than any experimentations just being trialled in a special or beta build). There are other configuration files for more sophisticated options such as how Cumulus communicates with external reporting systems.
You may find the Cumulus_Screenshots help you, although note the screens may relate to a different software version/build to that you are using.
Location panel
Pay attention to the box labels, enter unsigned integers for degrees, minutes and seconds, then add either N or S for Latitude and either E or W for longitude.
Units of measure panel
By far the biggest decision you will make, and be held to, is the various units of measure. Select these very carefully when you are setting up.
Remember if you try to change your old data later it probably has already been rounded and applying a single conversion factor would cause inaccuracy. For instance in rainfall you can't get back exactly to millimetres to 1 decimal place from inches to 2 dp. For example, 0.01 inches is 0.254 millimetres, which rounds to 0.3 mm, but 0.02 inches is 0.508 mm, which rounds to 0.5 mm rather than 0.6. To minimise rounding error, you need to convert the old data first into whatever precision your weather station works in (e.g. Fine Offset rainfall bucket is 0.3mm, its pressure measurement is in dPa (integer decaPascal), wind speed in tenths of metres/second and temperature in tenths of degrees Celsius), this may be different to how you have set its console display, and then convert into whatever future units you select for Cumulus before rounding. So devising suitable conversion tactics and applying to all old data could require hours of work. See discussions in support forum e.g. this Fine Offset rainfall thread, this Vantage Vue wind speed thread or search (specify station or units).
Dates
Cumulus does require your computer SYSTEM short date to use a format with a separator between day, month and year in whatever format suits your region e.g. dd/MMM/yy, dd-MM-yy, MM/dd/yy and dd-MMM-yy are acceptable, but ddMMMyy is not suitable as a short date format with Cumulus. Any change to your short date format later is likely to give problems.