HOW CAN I CONNECT TWO LNB IN ONE RECEIVER

You must have a receiver with dual LNB inputs. Then you can switch between the two LNBs to tune in to different frequencies.

Not so. The most common way is by an inexpensive diseqc switch. Sometimes a 22 khz switch is used. One receiver input only required, but your receiver should have settings for diseqc and or 22 khz, Most do,

you need a handy LNB switch.