Merge branch 'FAQ_Docs_2' of https://github.com/DavisHenckel/ImportExcel into FAQ_Docs_2

FAQ/How to Write to an Existing Excel File.md

@@ -0,0 +1,32 @@
+# Write to an Existing Excel File
+### Enumerate the Excel File
+```powershell
+$ExcelPkgFile = Open-ExcelPackage -Path  "C:\Test\file.xlsx"
+```
+Contents of file.xlsx:  
+![ExcelFileContents](/images/FAQ_Images/ExcelFileContents.png)
+### Enumerate the Worksheet to View or Modify the Data
+```powershell
+$WorkSheet = $ExcelPkgFile.Workbook.Worksheets["sheet1"].Cells #open excel worksheet cells from worksheet "sheet1"
+```
+Visual of Data Structure:  
+![DataStructureExcelPkg](/images/FAQ_Images/DataStructureExcelPkg.png)
+
+Modify a specific value by accessing row/col like a 2D Array:
+```powershell
+$WorkSheet[1,4].Value = "New Column Header" #Starts at index 1 not 0
+```
+Contents of file.xlsx after modifying:  
+![ExcelFileContentsPostAdd](/images/FAQ_Images/ExcelFileContentsPostAdd.png)
+Can also load a value at a specific index:
+```powershell
+$ValueAtIndex = $WorkSheet[2,1].Value #Loads the value at row 2, column A
+```
+```$ValueAtIndex``` now contains: ![ValueAtIndexData](/images/FAQ_Images/ValueAtIndexData.png)  
+### Save File After Modifying
+The changes will not display in the Excel file until Close-ExcelPackage is called.  
+```powershell
+Close-ExcelPackage $ExcelPkgFile #close and save changes made to the Excel file.
+```
+**Note**: If the file is currently in use, Close-ExcelPackage will return an error and will not save the information.
+