can I put money into my inmate trust account before I enter jail

Yes, you can add just about any amount to your inmate trust account. But, beware that if you owe any restitution, court ordered payments, court costs, child support... anything that can be garnished will be garnished from that account if you place a noticable amount there. if you have nothing to worry about, deposit as much as you can. You will want to spend the max amount for commissary and telephone..