No worries.
As mentioned list your spec (or copy and paste the one i specced if it's the same) - just to be sure i know what i'm working with.
Before you switch on disconnect all the sata leads from the motherboard (don't unplug anything from the SSD/HDD), and one stick of memory. Also, clarify the slots that you've put the memory in - i'll specify the slots they should be in when you list your spec.
Also, be sure that you've plugged your monitor cable into the graphics card and not the motherboard - it's an easy rookie mistake.
And keep pressing that delete key on boot to access the BIOS - find the temp monitoring screen (manual) and report back with readings. Then we'll take it form there...
Once we've established temps are stable we'll flash the BIOS - which will involve that pen drive and the q-flash utility if you have the Gigabyte board. This will mean pressing <end> on boot - but will go inot more details tomorrow afternoon (maybe morning depends on when you're about).
My basket at Overclockers UK:
1 x Gigabyte GA-AB350M-Gaming 3 AMD B350 (Socket AM4) DDR4 Micro ATX Motherboard= £87.95
1 x AMD Ryzen 5 Six Core 1600 3.60GHz (Socket AM4) Processor - Retail= £188.99
1 x Corsair CMK16GX4M2A2400C14 Vengeance LPX 16 GB (2 x 8 GB) DDR4 2400 MHz CL14 XMP 2.0 High Performance Desktop Memory Kit - Black
1 x Gigabyte GeForce GTX 1070 Windforce 2x OC 8192MB GDDR5 PCI-Express Graphics Card= £419.99
1 x Super Flower Golden Green HX 550W "80 Plus Gold" Power Supply - Black= £69.95
1 x Hynix SL308 250GB 2.5" SATA 6Gb/s Solid State Hard Drive (HFS250G32TND-N1A0A)= £79.99
1 x Toshiba P300 1TB 7200RPM 64MB Cache High Performance Hard Drive (HDWD110UZSVA)= £38.99
1 x Aerocool QS-240 Micro-ATX Case - Black= £29.99
Total: £1,047.05
(includes shipping: £11.70)