[Grammar] Please help me to correct these sentences

[JRD]

How can we add theses items to the system again. These were added earlier but it does not show up in the system now. Please advise how can we make multiple changes on the items in the system. It is now very important because there are many items in the system, especially items in stock do not have the correct details. These details had already been updated, but they are now found missing, so we need to update it correctly.

 

[Tarheel]

Say:

How can we add these items to the system again?

And:

They were added earlier, but they do not show up in the system now.

 

[Tarheel]

Next sentence. Say:

Please advise about how we can make multiple changes to items in the system.

 

[Tarheel]

I don't understand the last two sentences.

If something is missing, you don't have it, so how can you update it?