User manager and GRANT permissions

Hello everyone, I hope someone will help me.

I am having problem with the users updating and changing tables. First, I have one client app that has user management and list of users, also I have HeidiSQL platform in which those users are listed. But, my Heidi username is not one of those in the list, so I have other username for accessing DB. My all users on the list are admins in that client that I need.

When I try to update something in the tables in DB, it returns errors like SQL Error 1142, command denied to user..

My question is how I change permissions, does it matter that my users are not the same? I guess my DB username is also admin.
How do I change permissions, privileges?

Thank you, I hope you get the question. I am pretty much new in this..
Racc

Tools/ User manager

I don't really understand the rest of the question. HeidiSQL does not have users of its own—it's nothing but a GUI client for another tool (MySLQ Server). And your application users are something you have designed—that's totally unrelated.

Thank you for reply.

When I go to Tools and User manager, it also gives me error, SQL Error 1227, again about privileges.

So, there is some other problem...