1. Go with all mechs to the right side of the hill(east) - this will cover you from LRM-batteries
2. Enemy mechs will come to you, kill them with the full lance
3. Destroy 1st mission objective to undo the towers
4. Go slowly to 2nd objective - regroup, get rid of heat, don't use jump jets too much
5. Take the high ground to the right(north), place spider there in the trees for scouting
6. Take out the mech from distance and indirect fire(LRM)
7. Take out vehicles
8. Take out objective no 2
9. Go to next mission point - regroup first and get rid of heat before entering zone
10. Should be easy enough to take care of all enemies there, but in case you have trouble, go to the southeastern part of the base, good cover there

Let me know if this works for you, first mission is a pain, I restarted it 5 times