What is the correct process to first book RCM expenses and then consolidate the voucher?.

You can pass RCM entries with purchase voucher entry. Kindly follow the following Steps: 
 Step 1: Go to transactions Menu click on Purchase voucher option. 
 Step 2: Under Purchase voucher click on Add. 
 Step 3: In Purchase voucher header select Series name, date, vch no. type. 
 Step 4: Select Purchase Type: Local-RCM / UnReg or Service Import-RCM or as required. 
 Step 5:and will get option for reverse charge: Compulsory or Service Import as required. 
 Step 6: Enter item details qty & price and general purchase entry details. 
 Step 7: Save Purchase Vouchers. 
 Step 8: Go to transction Menu Click on GST Misc. Utlities 
 Step 9: then Go to Check Post Consolidated RCM Payble Menu select the option Monthly Basis or Daily Basis as requried 
 Step 10: After Select the Month Click on ok 
 Step 11: In RCM payble Monthly Basis Windows Use Key F4 for post Consolidate RCM Payble Voucher 
 Step 12: Select Journal Voucher Series and Voucher Date then Click on Save 
 Step 13: In Consololidated RCM Payble Journal Voucher Screen Click on Save 
 Step 14: after Click on Save Click on Generate RCM Invoice No and Click on Save