Clean then well before re-using them. The threads are very fine, so a fine brush and a cleaning agent should get all the old thread lock out.
To tighten them up, turn on one clutch cover bolt on the edge of the flywheel and then use a OE spanner between a gearbox bolt and the clutch cover bolt to lock the wheel from turning.
Then use a torque wrench to do them up - in a star pattern order and up to 100NM each.
As mentioned, use a thread lock as well.
peter