various operating systems

It depends somewhat on what operating systems, and what you plan to do with them.

If it is various versions of Windows, start with the oldest. Finish with the newest.
Place the oldest on the C: drive, and each newer on a different partition / logical drive.

For Linux, you will need a boot manager.

Do not attempt to share application programs.
Install each application separately for each OS.

You can share data files.
I recommend setting up a separate logical drive to store your data on.

Chas

If you have partitioned your HD using fdisk from a boot-up disk, the boot-up disk will also have a format option. You should then format each of the partitions. The boot-up disk should also have a CD-ROM driver.
Assuming for example that you have created two partitions "C" and "D", then after installing the CD-ROM driver, at the DOS Prompt type "E" and press enter. When "E" appears at the prompt, type "setup," making sure the OS CD is in the drive. You will then be asked the desired path, which will be C:\ for the first partition.
If you have created the partition with a program such as "Partition Magic," you should follow the advice in the handbook.
I recommend System Commander as the easiest and most foolproof program for both creating partitions and installing different OSs in those partitions.
If your computer is new enough to support boot-up from CD, then that is another way to go.
In the above instructions, the parenthesis " are for clarification only. Do not type them inwith any commands.