1. Open the application (ex: CCleaner) that you want to change the processor priority level of.
2. Open Task Manager with more details.
3. If prompted by UAC, click/tap on Yes.
4. In the Processes tab, right click on the application (ex: CCleaner64.exe) or process from step 1, and click/tap on Go to details. (see screenshot below)
5. In the Details tab, right click on the already highlighted name of the file (ex: CCleaner64.exe) for the process from step 4, click/tap on Set priority, and click/tap on the priority level you want to run this application or process in. (see screenshot below)
6. Click/tap on Change Priority to apply. (see screenshot below)
7. Repeat steps 4 to 6 above for any other applications or processes you wish to change the priority level of.
8. When finished, close Task Manager if you like.