Acer Aspire One; How to instal programs with no CD/DVD slot?

Downloading from the internet is the usual method, or alternatively from a USB pen drive of sufficient size; for professionals from the network via the ethernet connection.

If you have the programs available only as CD's/DVD's either you can copy the contents to a USB pen drive using another computer that does have a CD/DVD drive, or alternatively buy an external CD/DVD drive.  Note that DVD's are bigger in capacity than CD's.

Also note that if trying to reinstall preinstalled programs, it may be possible to do so using the software stored on the computer - I don't remember now how the Acer One is configured in this regard, since it's been a while since I worked on one.

Good luck!

Clive