Not enough withheld

I recently realized my husband isn't having nearly enough taxes withheld from his paycheck. I'm afraid we're going to owe ALOT in taxes next year due to this.

1. how do we update the w4 to have more withheld?

2. is there a way to estimate what we should set aside come tax time since we are behind?

His salary is around 45k. I'm at 50k+ bonuses. We file married jointly.