If you have access to the DMG (if you're DMing, you're going to want it) page 57 has a chart listing how much XP an encounter of level X for a group of 4, 5, or 6 PCs should be. You ought to be able to modify this for a group of 2 fairly easily by taking the XP for a 4-person encounter of the level you want and dividing by 2.
In case you don't have it handy, here are the XP totals for a group of 2 for the first 10 encounter levels:
Remember that not every fight should be the same level as the party. Fights of the party's level are average difficulty (or easy if the party is optimized), fights of lower than the party's level are easy (or speedbumps at best if the party is optimized), and fights that are higher than the party's level are hard (how hard again depends on party optimization). Generally any fight of less than party level -2 or -3 is too easy, and any fight of party level +4 or more is too hard for all but heavily optimized parties. The same range also applies when selecting monster levels, so monsters should be within 3 levels of the party; a single regular level 10 monster might be the right amount of XP for a level 1 encounter (in a 5-person party), but its defenses and attack values will be much higher than the party's.
Thus, if you want a typical fight for a level 1 party with 2 PCs, you should use 200xp worth of monsters. If you want a challenging fight for a level 1 party with 2 PCs, you should use 300xp of monsters. You can compare a fight's XP total to the recommended XP for a 5 person to estimate what level the Kobold Hall fights should be, then turn it into an appropriate fight of the same level for a 2-person fight.
That said, paladin and warlord is a relatively good 2-person combination (as long as the paladin has a good MBA), so you might find that you need to add in a little extra XP worth of monsters. If you find that adding monsters makes combat take too long (paladin & warlord combo has a lot of healing, but isn't a damage powerhouse), try going back to the normal number of monsters, but double their damage and cut their HP in half.