[Micah Foehammer]

You should see at least one half moon crescent icon in the action bar along the lower part of the screen. If not, try right clicking on the search or hide functions (look like a magnifying glass or a figure in silhouette respectively) and a bar of selectable options will appear. Left click on the half moon and that will put a generic spell slot into the option slot you selected. To assign spells, right click again and your spell menu should appear. Left click on the spell to assign it to the magic slot.

However, what I SUSPECT may be happening is that your wisdom is too low. All spellcasters need a sufficiently high prime casting attribute in order to cast spells (wisdom for clerics, intelligence for mages, etc.) In order to cast clerical spells of level X, your fighter / cleric will need a wisdom of 10 + X (i.e. if you want to cast 9th level spells you need a wisdom of 19). If your wisdom is BELOW 10, then you can not cast clerical spells at ALL! If that is the case and you are determined to play a fighter/cleric, the only option is to ditch him and rebuild him from scratch.