You are in "first seat". This is another jargon term. It means you are the person left of the dealer, and hence the first person to bid. What should you bid?
Let's assume that you want to "tell" your partner that you have 20 meld. The way to do this is to add 2 to the current bid. But there is no current bid, so what does this mean? The default minimum bid is 50. So add 2 to 50, and give a "meld bid" of 52. Any player who knows about meld bids will understand that your hand contains about 20 meld. Note: that includes your opponents! You are giving your partner information, but at the cost of revealing information to your opponents as well.
You may have noticed that Mr Pinochle has a "run" in hearts in the screenshot above. He has a card of each rank in that suit: A-10-K-Q-J. If hearts were the trump suit, he would get additional meld due to the run. However, such additional meld should never be added to your meld bid. Only meld that is independent of a trump suit should be used for making a meld bid.
Are you confused about why you added 2 to the current bid above? It's because you had 20 meld. The rule for giving a meld bid is:
Here is an example where you are "second seat" (second to bid). You have 52 meld - that's a lot of meld!
If your right-hand opponent (C-3PO in the screenshot) had passed, your meld bid would be 55. However, that player bid 52 - and in doing so, revealed that he has about 20 meld. If you want to give a meld bid, you will have to add 5 (52/10) to the previous bid. That means your bid should be 57. Sometimes, in discussions, people will say "your meld bid is +5" in this case. But you should never say this out loud at a Pinochle table! Signalling is never done verbally, with Pinochle.
In the screenshot below, Mr Pinochle should not give a meld bid. There are a couple of reasons. Can you spot them?
You can read more discussions about bidding here: