2
Depends on what version of XOOPS you're using.
If your'e using 2.2 and up, go into your admin section. Click on "Blocks." A submenu will appear that says, "List All Blocks." Click on it.
You'll be taken to a page that gives you options about displaying all of the blocks for each module. You may or may not see them all.
Use the drop-down menu to add your blocks to the pages you want them to display on. To create a custom block, look for System and then Custom Blocks.
If you're using XOOPS 2.0.13 or below, just go into your admin section. There should be an icon on the left column that says, "System." Click on it and choose "Blocks" from the next menu.