How to add picture/screen to post

Hi,  don't know where to ask this.

 

How do you all put a screen shot into a post?  I had it in the clipboard.  I got it into Word and tried to copy into my post but the paste was greyed out and ctl v didn't work.  I put it in paint and saved it with a name but couldn't copy the file I made to here either.  I use a very old Snag-it program to make screen prints.  I don't know how any other way, like in XP. 

 

Christine

Dimension E520 Desktop
MS Media Center Edition 2005 - Current
Intel Core 2 Duo processor E6300
2GB dual-channel DDR2 SDRAM
Integrated Audio - SigmaTel High Def
Video - NVIDIA GeForce 7300 LE
320GB HD
D: is Philips DVD-Rom DROM6316
E: is NEC DVD+-RW ND-3650A
Monitor is E207WFP

Inspiron 6000
Win XP sp2 - Current
Intel Pentium M 730 (1.6ghz/2MB)
Accelerator 900 Graphics
80GB HD
Intel PRO/wireless 2200

Comcast Cable Modem to Alpha Shield firewall to Netgear Router. Wireless to Inspiron 6000 and wire to Dim E520.