After the buyer submits the SOW, the status shows as "Pending Supplier Review". This means the SOW is sitting with the supplier, who is in the process of reviewing it. If collaboration is enabled, the supplier and buyer review can go back and forth as many times as needed until mutually agreed upon between both the buyer and supplier.
After that happens, if the buyer has enabled the ability for the supplier to include workers on the SOW, the supplier can begin adding their SOW Workers to the worker roles that are identified on the SOW.